ENH: Added KWSYSPE_DEBUG macro to print debugging trace information.  Added TODO comment explaining why process execution can still hang when a grandchild keeps the output pipes open.
ENH: Added KWSYSPE_DEBUG macro to print debugging trace information.  Added TODO comment explaining why process execution can still hang when a grandchild keeps the output pipes open.

chuckatkins/KWSys,chuckatkins/KWSys,chuckatkins/KWSys,chuckatkins/KWSys