Max task par fixes

This fixes several failures associated with https://github.com/chapel-lang/chapel/pull/156. The specific changes are as follows.

runtime/src/chplsys.c
Fix a failure in modules/standard/machine/numCores: the scheduling affinity used to determine how many PUs there are on the node should be that for the calling process, not pthread.

test/localeModels/gbt/maxTaskPar.prediff
Fix a failures localeModels/gbt/maxTaskPar: treat cray-xc and cray-xe targets in the same way as linux ones, and use hwloc's lstopo utility to produce the .good file for locModel=numa and tasks=qthreads.