Add CHPL_GASNET_SEGMENT to the gen directory hierarchy so that we can have fast and everything built for a particular substrate at the same time.
Add CHPL_GASNET_SEGMENT to the gen directory hierarchy so that we can
have fast and everything built for a particular substrate at the same
time.

WARNING: If you have an existing GASNet build, you will need to
rebuild the runtime after updating with this commit.  I guess you
could rearrange the directories, but that seems like more work than
it's worth.



git-svn-id: 88467cb1fb04b8a755be7e1ee1026be4190196ef@19396 3a8e244f-b0f2-452b-bcba-4c88e055c3ca

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