PTX: Add intrinsics to list of built-in intrinsics, which allows them to be

PTX: Add intrinsics to list of built-in intrinsics, which allows them to be
     used by Clang.  To help Clang integration, the PTX target has been split
     into two targets: ptx32 and ptx64, depending on the desired pointer size.

- Add GCCBuiltin class to all intrinsics
- Split PTX target into ptx32 and ptx64

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129851 91177308-0d34-0410-b5e6-96231b3b80d8