Should fix build errors with 'make contrib'.

Continuation of 36c30487

Bug 6782

Bug 6633.

Regression in eee05efb.

Bug 6801.

Bug 6920

Bug 6290

Bug 6791

Bug 6791

Bug 6791

This is to prevent defaults from overriding the incomplete set of options
that have been populated from the environment, vs. some options that will
be determined from job_desc_msg_t once fetched from the controller.

The post_submit() hooks integrate jobid/stepid information to allow
detailed logging - requires pre_submit() to generate an intermediate
message while the option data is still in the most raw form, which
the plugin can save and post_submit() can then log as needed.

Since post_submit() cannot safely read datastructures, plugins will
need to store data between pre_submit and post_submit. Since calls
are done multiple times - once per jobpack - need to allow plugin
to keep state in terms of which pre/post submit calls are for which
job pack.

The cli_filter pre_submit() hooks are the primary location for cli_filter
read and processing of options.

These allow a plugin to change the default values for the cli options to
different values based on site policy or user needs.

Moved spank_init_post_opt() calls to just before cli_filter pre_submit
hooks in service of that.

These are primarily intended to allow cli_filter plugins to generically
get and set values for any given option. They are implemented here because
the slurm_cli_opt_t datastructure and common_options data structures are
statically defined within slurm_opt.c.

Use lib_LTLIBRARIES instead of pkglib_LTLIBRARIES to avoid being installed
under the lib/slurm/ directory.

Change to -shrext .so.2 -avoid-version to install once, and avoid libtool's
automatic versioning. (Idea borrowed from nss-mdns's Makefile.am .)

All glibc nss interfaces need to be installed as revision 2 at this time,
thus the hard coded -version-info.

After 083c48b8 these are sent as part of the launch cred, and only sent
as part of launch_tasks_request_msg_t / batch_job_launch_msg_t is send_gids
is disabled. (In which case the slurmd will populate them instead through
these structs, since it cannot alter the launch cred.)