Update srun and sbcast man pages and help messages for compression
  library argument.

Relies on Linux-specific behavior of setfsuid/gid, so disable on other
platforms for now.

Fix linking issues to only have the compression libs link to file_bcast which intern get pulled in my anyone linking to the .la.

Move compression stuff over to the file_bcast lib, so we only have to link directly with that and not pull libs all over the place.

- Fix issue where max_out calculation for zlib was incorrect - use
  deflateBound to properly calculate required buffer size, 1024 is
  not sufficient padding for uncompressable input.

- Work towards sending file offsets across the wire in preparation
  for mmap'd output for lz4.

Rather than compressing at most block_len into a message, compress up to
(10 * block_len) into a single message.

10x arbitrarily chosen to mitigate buffer issues when uncompresssing in
slurmd.

Testing against a 100MB zero file, this reduces the messages required from
13 to 2.

Regression in last commit required zlib to send each chunk as a
separate block, rather than packing multiple chunks per block.

1) Use mmap'd I/O.
2) Move buffer handling down to the individual compression routines.
   This will eventually allow them to read more than buffer_len at a
   time in order to emit a buffer_len message, and thus minimize the
   number of messages send. (Current logic sends the same number of
   messages, but the payload for each can be compressed. I expect
   more performance gains are available by limit the message count.)
3) Move buffer_len to a global, and change function signatures.

Move files from common to new dir location for bcast. This also sets up the 3 locations that need to be linked to compression libs.

And switch CHUNK macro -> chunk within the function.

Add orig_len to data structure to avoid guessing uncompressed size. Have
zlib use this as well to avoid xrealloc() calls. (Future improvement to
zlib would avoid use of the temporary buffer + memcpy calls.)

Note that this is handling each block independently. Stream mode would
be better, switch to that in the future for additional performance gains.

Also change sbcast info line to print type as int rather than as bool.

Note one quirk - SLURM_COMPRESS env var must be set to a type. Setting
to 'true' or '1' will not work, when it would have enabled zlib before.

If no type given current default is zlib. 'lz4' and 'zlib' are the only
two types supported currently. Print an error if unknown type given, but
continue with compression disabled.

Stub out lz4 functions, will need to be filled in later. sbcast/srun also
need work to allow them to specify compression routine.

When a node's MCDRAM configuration changes, the amount of High
Bandwidth Memory (HBM) changes also. HBM is treated like a GRES
that can be allocated to jobs, so we update each node's GRES
value when its MCDRAM configuration changes.

Just in case some job fails to terminate as expected.

# Conflicts:
#	src/plugins/burst_buffer/cray/burst_buffer_cray.c

gang scheduling before doing code for gang scheduling.

burst_buffer/cray: Set environment variables just before starting job rather
    than at job submission time to reflect persistent buffers created or
    modified while the job is pending.
bug 2545

buffer is found.

Bug 2576

What happened was a function was doing a double read lock which isn't
awesome to begin with, but not really horrible (if all you are doing is
read locks anyway).  The problem was after the first lock was locked a
different thread was going for a write lock and so when the second
read lock came in it created deadlocked.

Coverity 77851.

Jobs below the specified threshold will not have resources reserved for them.
bug 2565

Avoid possibly aborting srun that gets simultaneous SIGSTOP+SIGCONT while
    creating the job step. The result is that the signal hanlder gets a
    argument (the signal received) of zero.

Here's a log, window 1:
$ srun hostname
srun: Job step creation temporarily disabled, retrying
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 18
srun: I Got signal 0
srun: Cancelled pending job step

Window 2:
$  kill -STOP 18696 ; kill -CONT 18696
$  kill -STOP 18696 ; kill -CONT 18696
$  kill -STOP 18696 ; kill -CONT 18696
....

bug 2494

Copy logic from select/cons_res to select/serial that is equivalent
to commit ec50cb2f