regent: Support fast atomics for CUDA on newer LLVM versions.
regent: Support fast atomics for CUDA on newer LLVM versions.

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