"srun output overflow ("Need to rewind" in srun/_do_output_line)"

When srun's stdout is consuming data slowly, srun can receive notice that
the job has terminated before the output stream has been fully written.

The IO thread will receives a SIGHUP to kick it out of its blocking poll.
However in the slow stdout situation the SIGHUP can interrupt the
fflush.  When the fflush is interrupted, it appears to clear the stream
buffer even though the data wasn't written out to the file descriptor,
and we see data loss on stdout.

To avoid this situation, this change makes signals to the IO thread
go over a pipe rather than sending a signal.  Also, some extra return
code checking is done in io.c:_do_output_line().

under AIX.  This work-around bypasses the eio handling of /dev/null and
instead directly makes pin[0] a file handle for /dev/null.

The only problem with this fix is that it is not obvious elsewhere in the
code that pin is not a pipe when using "srun --batch" and stdin is
/dev/null.

    terminating).

systems (different mechanisms to prevent line-feed).

    var (if set).

slurm_job_node_ready API), prolog and epilog exit immediately.

access the BGL Bridge API.

made it so when making new partitions it will try to create them multiple times if it fails in the api.

based upon feedback from RobinG and NCAR.