Made some changes to the PBS launcher
Made some changes to the PBS launcher

Improved the PBS launcher for NCCS by making it more useful for
queues other than the debug queue.  In particular, I:

- removed the assumption that the debug queue is the default to
  use if the user doesn't specify a queue.  While this was appropriate
  when we were in an early development mode, it isn't appropriate for
  all Chapel users to run codes in debug by default -- it should be
  explicitly specified using CHPL_LAUNCHER_QUEUE

- added support for specifying a walltime to the NCCS version of qsub
  via CHPL_LAUNCHER_WALLTIME.

- if the user specifies neither a walltime nor a queue, an error is
  printed out explaining that they must set one of these.

Thanks to Srinivas Sridharan for bringing this issue to my attention
and supplying a proposed solution.




git-svn-id: 88467cb1fb04b8a755be7e1ee1026be4190196ef@15858 3a8e244f-b0f2-452b-bcba-4c88e055c3ca

CoryMcCartan/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,hildeth/chapel,sungeunchoi/chapel,hildeth/chapel,sungeunchoi/chapel,chizarlicious/chapel,sungeunchoi/chapel,chizarlicious/chapel,sungeunchoi/chapel,chizarlicious/chapel,hildeth/chapel,chizarlicious/chapel,CoryMcCartan/chapel,hildeth/chapel,hildeth/chapel,sungeunchoi/chapel,chizarlicious/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,chizarlicious/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,hildeth/chapel,CoryMcCartan/chapel,hildeth/chapel,chizarlicious/chapel