_entity_add_data() in src/common/entity.c defined as "static" to avoid
    confusion with same function name in src/common/layouts_mgr.c
_entity_get_node_walkfunc() in src/common/entity.c defined as "static"
Removed redundant set of "rc" variable _layouts_autoupdate_layout_if_allowed(),
    src/common/layouts_mgr.c
Initialized variable "rc" in _layouts_read_state(), src/common/layouts_mgr.c
    in case the named file does not exist (stat() returns an error)
The CLANG tool reported a possible error in _autoupdate_layout_tree(),
    src/common/layouts_mgr.c in the event that xtree_node_get_data()
    returns a NULL value and that pointer is used later in the function for
    "cnode->entity". I added "return 1" if xtree_node_get_data() returns NULL,
    but am not yet sure if that is the correct action.
The CLANG tool reported possible errors related to a NULL value pointer in
    s_p_parse_pair_with_op(), src/common/parse_config.c which have been fixed.

Having MAX_PREFIX_CNT to 1k limits the number of elements that can be
expressed using expressions like node[1-1025].ib[0] to 1024.

As 64k is the max number of nodes that can be handled by Slurm, increase
that value to 64k in order to be able to express at least that number of
elements using a[x]b[y] when y is the same value for all the elements.

Note: also required by the layouts parsing logic when parsing float values
in expressions like : 'Entity=node[1-64000] FloatKey=[1-64000].[0]'

layouts plugins inheritances among entities KVs like KEYSPEC_UPDATE_CHILDREN_SUM
(see layouts_mgr.h) are now fully managed by the layouts manager.

An extra third stage is added while loading the configuration and state
informations during startup in order to automatically update the layouts
entities KVs based on the relationships defined in the plugin among the keys.
The third stage is executed right after the second one that is in charge of
establishing the relations among the entities.

When an update is performed using the API laouts_update_layout call, the
autoupdate logic is also applied.

Note that a layout plugin must explicitely ask for autoupdate support by the
layouts manager using the autoupdate field of its layouts_plugin_spec_t internal
structure 'plugin_spec'.

layouts API calls using the push/pull logic also leverage the autoupdate
mechanism.

Note that for now, the autoupdate is "full" whenever it is called.
Improvements should be considered in the future to improve the performance
of the logic when possible, especially in push/pull contexts.

> layouts_entity_{set,get,setpush,pullget}_kv[_ref] calls

These new calls enable to perform the get/set operations on the key/value pairs
of a particular entity in a defined layout. The push/pull operations enable to
call for the automatic update of the linked entities in the layouts (i.e. parent)
for push and for the automatic update of the requested entity using the linked
entities information for pull.

Note that 2 variations are proposed for each call, differentiated by the _ref
suffix. When _ref is suffixed, then the calls only deal with references and no
copy of the data is performed, only data references (pointers) are set/get. The
_ref suffixed calls should then be considered as more efficient but can lead to
issues if the pointers are modified after the get operations occur but before
their real use. For that reason, layouts_{lock,unlock} calls would certainly
appear in a next commit as well as _nolock suffixed calls in order to better
handle those scenarios.

Note that the ...pull/push... calls are just stubbed in that commit. The logic
will be added later.

> layouts_entity_get_mkv[_ref] calls

These new calls enable to perform the get operations on a set of key/value pairs
of a particular entity in a defined layout. (mkv stands for multiple k/v pairs)

When _ref is suffixed, then the calls only deal with references and no copy of
the data is performed, only data references (pointers) are got. The _ref suffixed
calls should then be considered as more efficient but can lead to issues if the
pointers are modified after the get operations occur but before their real use.

For that reason, layouts_{lock,unlock} calls would certainly appear in a next
commit as well as _nolock suffixed calls in order to better handle these
scenarios.

The previous logic directly associated xtree_node_t elements with entities.
The list of nodes associated to an entity was thus directly made of xtree_node_t
elements each one pointing directly to the entity.

An entity being layout agnostic, that is to say not bound to a particular layout
it was not possible to look for the xtree_node_t element associated with a
particular layout in an entity. This was due to the fact that the entity_node
element was not used as an intermediate level to link the entities and their
different xtree_node_t elements. Indeed, this is the role of the entity_node to
associate a position in a particular layout with an entity.

The new logic ensures that when building a layout relational structure :

- (1) an entity node associated with the targeted layout is created for the
  entity and references both the layout and the entity it is associated too.
- (2) the entity node is the element that is added to the (tree) relational
  structure of the layout resulting in the creation of a relational node
  (xtree_node_t) that will reference it directly.
- (3) the created relational node (xtree_node_t) is referenced in the associated
  entity node in order to provide a way to go back to the position in the
  relational structure from the entity node, thus enabling to search the
  neighborhood of an entity for a particular layout only knowing the entity
  and the layout to look at.

The packing logic was modified to take into account the new level of indirection
(the entity_node element) when walking the relational structure of a particular
layout. The debug dump logic was modified too to reflect the changes.

Layout entities Key/value pairs were automatically merged during updates with
the previous logic. It is still the case by default but keyspec can now
also be declared as RDONLY in layouts plugins in order to avoid that.

Note that RDONLY keys can still be written by the plugins implementations when
necessary. It only affects the automerge logic avoiding to let administrators
update them with 'scontrol layouts update ...' commands directly.

it does not provide any information and make things longer than necessary.

layouts_update_layout(...) now enables to process an incoming buffer containing
a contiguous set of packed strings and push that information into a particular
layout. Only the entities key/value pairs are updated for now.

layouts_p_update_done is a new callback that will be triggered with an array of
entities pointers when an update is performed on a particular layout. This
callback will help layout plugins to perform various consistency checks and/or
update any internal states that should be updated based on the modified entities
information.

No information concerning the udated key/value pairs are provided for now.
For finer-grained controls over what has changed, the plugins will have to use
both the parse_entity callback and the update_done callback to handle what has
changed and what should be rebuilt after the update for now.

layouts_update_layout(...) now enables to process an incoming buffer containing
a contiguous set of packed strings and push that information into a particular
layout. Only the entities key/value pairs are updated for now.

layouts_p_update_done is a new callback that will be triggered with an array of
entities pointers when an update is performed on a particular layout. This
callback will help layout plugins to perform various consistency checks and/or
update any internal states that should be updated based on the modified entities
information.

No information concerning the udated key/value pairs are provided for now.
For finer-grained controls over what has changed, the plugins will have to use
both the parse_entity callback and the update_done callback to handle what has
changed and what should be rebuilt after the update for now.

see 024c9fab036c8e6110b9276367dcf875a81876ef

> add a new 'operator' field in s_p_values_t

Provide the capability to manage key[+-*/]=val entries in the parsing logic.
A new operator field now enables to know which operation is associated to
a pair of key/value instead of the classical set. Introduced operators are
provided by the slurm_parser_operator_t type with the following value :

 * S_P_OPERATOR_ADD
 * S_P_OPERATOR_SUB
 * S_P_OPERATOR_MUL
 * S_P_OPERATOR_DIV
 * S_P_OPERATOR_MIN
 * S_P_OPERATOR_MAX
 * S_P_OPERATOR_AVG

It is the caller of the parsing logic that is responsible of using that
information in order to act as requested. The parsing logic do not do any
computation based on the extracted operator.

S_P_OPERATOR_{MIN,MAX,AVG} are internal operators not yet bound to particular
char in the parsing logic of 'key[operator]=val' entries. They are only used
for layouts internal logic.

Why:

Introducing the layouts framework, the parsing logic of SLURM was extended to
manage efficiently conf elements expansions. Layouts heavily rely on the SLURM
parser to tansform textual configurations into internal representations.

Looking at a way to provide live update of Layouts information, it was
interesting to reuse the parsing logic of SLURM instead of trying to do the
same thing somewhere else.

Introducing a "key[+-*/]=val" feature was thus mandatory in order to apply
numerical modifications of the layouts internal states on the controller side
instead of trying to compute that on the client side and then send the updated
information, loosing the capability to perform operations atomicallly.

> add S_P_{FLOAT,DOUBLE,LONG_DOUBLE} and related s_p_get_* functions

> enable true/false string parameter with S_P_BOOLEAN

Layouts logic was using true/false instead of yes/no|0/1|up/down
that were supported with S_P_BOOLEAN. Add true/false instead of reverting
to one of the already available parameters as it was strange to not have them.

> add "_." as valid characters in key names

> add s_p_parse_buffer to parse configuration lines from a Slurm Buffer

s_p_parse_file is a convenient way to handle the parsing of Slurm configuration
file. It however only works with traditional file and can not be used to process
a bunch of configuration strings.

s_p_parse_buffer provides the capability to parse a bunch of contiguous strings
packed into a Buf type, stopping the processing at the first unsuccessfull
string extraction from the buffer.

Add a stage 1.1 in the loading of the layouts in order to recover the updated
entities prior to building the relationships among them (stage 2) using the
states saved in Slurm state save location for the layouts to load.

Information concerning the relations among entities provided by the 'Enclosed'
conf pragma are not taken into account for now when reading from layouts state
files. No layout plugins callbacks are called when doing that for now.

Add a function to help packing a particular layout into a Buffer as a set of
strings terminated by a "\0" string and representing the current expanded
form of the layout configuration as it could be described in a standard conf
file.

Use that function to provide a state save logic generating expanded conf files
in the state save location, one file per generated layout. Entities not linked
to a particular layout at save state time will not be saved as considered as
no longer necessary.

Note that the tree structure of the layouts are also saved in the packed
information as well as in the generated expanded file.

Note: fix a bug when freeing layouts in slurm_layouts_fini along the way.

The layouts_keydef struct only stored the associated key name prefixed by
the type of layouts (or mgr) inorder to have a unique identification of
all the keydefs in the central hash table.

To help accessing the original key name as specified in the layout conf
file, the shortkey field now stores a copy of the original key. This is
a short increase in the memory footprint of the layouts_keydef struct but
as this structure is only allocated once per key in a layout, the global
overhead is very small but provides an efficient way to retrieve the key
name.

SPANK naming changes: For environment variables set using the
    spank_job_control_setenv() function, the values were available in the
    slurm_spank_job_prolog() and slurm_spank_job_epilog() functions using
    getenv where the name was given a prefix of "SPANK_". That prefix has
    been removed for consistency with the environment variables available in
    the Prolog and Epilog scripts.
bug 1570

No change in logic

Requests by normal user to reset a job priority (even to lower it) will
result in an error saying to change the job's nice value instead.

Conflicts:
	src/slurmctld/job_mgr.c
	src/slurmctld/job_scheduler.c

A non-administrator change to job priority will not be persistent except
for holding the job. User's wanting to change a job priority on a persistent
basis should reset it's "nice" value.
Without this change a user might lower a job's priority, but Slurm will
not lower it more based upon fair-share changes.

Increase the MAX_PACK_MEM_LEN define to avoid PMI2 failure when fencing
with large amount of ranks (to 1GB).