1. Simplification by generating the indices via the built-in ipairs function.

 2. Avoid encountering an error when trying to unset job_desc fields by
    assigning the  special Lua value `nil':

    [2011-04-23T13:28:51] error: job_submit/lua: /opt/slurm/default/etc/job_submit.lua:106: \
			bad argument #3 to '_set_job_req_field' (string expected, got nil)
    The error is avoided by testing for a nil value and using an empty string instead.

Tested script to work after applying changes.
Patch from Gerrit Renker, CSCS.

Found while reading mgr.c, often MAXPATHLEN is 1024, but not sure it is always.
Patch from Gerrit Renker, CSCS

This adds user documentation on how memory is specified by ALPS (per-PE share) and SLURM
(per-node or per-CPU units), clarifying the correspondence.
Since it is a correspondence, but not a direct equivalence, the patch also removes the
PBS-script directive support for 'mppmem', since otherwise it would lead to unexpected
behaviour. From Gerrit Renker, CSCS.

Conflicts:
	src/plugins/select/cons_res/select_cons_res.c
	src/plugins/select/linear/select_linear.c

New function added: count_job_resources_node(job_resources_t *job_resrcs_ptr,
				    uint32_t node_id);
/* Return the count of core bitmaps set for the specific node */

nodes IF its resources have been merged into another job.

nodes IF its resources have been merged into another job.

Conflicts:
	NEWS

Added the ability to save the job's comment field to the Accounting Storage Database

 - Renamed the Accounting Storage database's "DerivedExitString" job field to
    "Comment".  Provided backward compatible support for "DerivedExitString" in
    the sacctmgr tool.
 - Added the ability to save the job's comment string to the Accounting
    Storage db (to the formerly named, "DerivedExitString" job field).  This
    behavior is enabled by a new slurm.conf parameter: AccountingStoreJobComment
 - Updated tests 7.13, 7.14 and the html pages to reflect renaming of the
    DerivedExitString to Comment

fixed aprun to be called from the local path as opposed to where slurm was installed in the srun wrapper.