Cleanup the JIT as per PR176. This renames the VM class to JIT, and merges the

Cleanup the JIT as per PR176.  This renames the VM class to JIT, and merges the
VM.cpp and JIT.cpp files into JIT.cpp.  This also splits some nasty code out
into TargetSelect.cpp so that people hopefully won't notice it.  :)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10544 91177308-0d34-0410-b5e6-96231b3b80d8