fixed ISPC compilation fail caused by the change of llvm::Value to llvm::Constant in DIBuilder member functions (LLVM commit 222070)
Merge pull request #906 from ncos/ispc_build_fails

fixed ISPC compilation fail caused by LLVM DIBuilder API change
Tracking LLVM trunk: SmallPtrSet changes
Merge pull request #908 from dbabokin/trunk

Tracking LLVM trunk: SmallPtrSet changes