"Scontrol abort" works. It was leaving a hung pthread due to a recent
   change.
Fix a couple of potential memory leaks
"switch_type" has been added to config data structure, un/pack, etc,
   but not yet reported to the user or documented yet.
The plugins now use function calls to get a their type and plugin directory
   from a common data structure rather than individually reading and
   parsing the configuration file.

   an assumption of tabstop=4
 o Try not to let lines exceed 80 chars
 o Replace calls to error() with verbose() to avoid unexpected messages to
   stderr in API clients.

Streamline the API: eliminate activate() and fold it into a new create(), rename free() to destroy(), make unpack() return an allocated credential instead of being passed a 'blank' one

 o src/slurmd : do not bother to sleep full timeout in rpc_timelimit
   if the job step goes away on SIGTERM.
 o src/common/slurm_auth.c : get default plugin dir from SLURM_PLUGIN_DIR
   rather that always "/usr/local/lib/slurm"
 o other small fixes