Provide for querying the sublocale requested when a task was created.

[Reviewed by sungeun.]

In the NUMA locale model currently under development we have found it
useful to be able to determine what sublocale was requested at the time
a task was created.  This commit records in task private data the subLoc
argument to chpl_task_addToTaskList() and chpl_task_startMovedTask(),
and adds the function chpl_task_getRequestedSubloc() to retrieve it.  It
also makes chpl_task_setSubloc() change the stored requestedSubloc.

While here, I also did some cleaning up in tasks-qthreads.c, removing
some definitions that should have come out in r21856, when I removed the
unused task private here pointer, locale ID, and allocation function
pointers.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@21891 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
initial commit of version using miniMD's modified BlockDist

git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@21892 3a8e244f-b0f2-452b-bcba-4c88e055c3ca