replace with usleep and flags

from michal novotny

    ESLURM_INVALID_NODE_COUNT to better reflect its meaning.

    and additional info

    maximun node counts of pending jobs (the operation was previously 
    restricted to user root)

  credential and was failing to subtract an offset where appropriate - offset used to distingush
  munge errno from slurm errno)

    drained).

    job's time limit).

add warn_signal and warn_time to slurmctld job structure.
save/restore the job parameters in slurmctld and add
stub to perform the signal

    notify programs before reaching the end of their time limit.
    (So far, just document the option and get it from the command down
    to slurmctld. More to come later.)

  job's Eligible Time now StarTime

  accounting for job_start (called in some cases when pending).
  restore start_time after accounting (it's the expected
  start_time for pending jobs). 

   use of errno to pass around information

Expand explanation of recent change in NEWS.

    the queue SLURM searched in an attempt to backfill jobs, default value 
    is 50 jobs.

CompleteWait configured to 0 (default). Change to wait.

from END to END_TIME

  as a return code from the terminate job RPC

  after that, kill the job