Changes to salloc:

  - returns the return code of its child command
  - add timeout for limiting how long it waits for a PENDING job allocation
    (slurm_allocate_resources_blocking was updated to timeout correctly)
  - cleans up job allocation on Ctrl-C (Actually, it ignores SIGINT, SIGTERM,
    SIGQUIT, but unblocks them for the child, so ctrl-c from the shell
    hits the whole process group, and the child exits, and salloc cleans
    up like normal.  Might to be more proactive with signals, but I
    am not yet certain.)
  - trim more unnecessary command line options
  - man page additions