regent: Do not emit NVVM intrinsics unless we're on LLVM 3.8
regent: Do not emit NVVM intrinsics unless we're on LLVM 3.8

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion