[clang] [clang][libclang]Check auto type for type constraints (PR #172472)

[Aaron Ballman via cfe-commits]

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

Thank you! The changes LGTM but this should have a release note in `clang/docs/ReleaseNotes.rst` so others know about the new API.

https://github.com/llvm/llvm-project/pull/172472