Added semaphores for some job_step functions that were lacking them.

 o do not block all signals

 o call log_reinit() after fork() in pthreaded app to reinit log mutex,
   but keep same log options.

 o inserted comments in some areas of confusion or possible problems.

go through and create core files/terminate.

rather than the job table). Other minor clean-up.

 o reformat for consistency with the rest of slurm code

This makes for simpler/safer cleanup.

   to initialize qsnet and run test job

   into line with rest of slurm

 o some error message cleanup

 o Some error and debug message cleanup.

Major revisions to agent.[ch] - still under development

version).