[clang] [HLSL] Add NativeInt16Type langopt to control whether short type is supported. Enabled by default for all but HLSL. (PR #165584)

[Justin Bogner via cfe-commits]

https://github.com/bogner approved this pull request.

LGTM. A couple of take-it-or-leave-it comments inline.

https://github.com/llvm/llvm-project/pull/165584