Don't use polling threads for Portals GASNet
Don't use polling threads for Portals GASNet

Add a new variable to the comm init function called needPollingThread. It
is initialized to one. If GASNET_CONDUIT_PORTALS is defined, set it to zero.
Instead of always creating it, only create it if needed.


git-svn-id: 88467cb1fb04b8a755be7e1ee1026be4190196ef@14004 3a8e244f-b0f2-452b-bcba-4c88e055c3ca

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