[clang] Lex: add support for `i128` and `ui128` suffixes (PR #130993)

[Hans Wennborg via cfe-commits]

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

> We use existing support for the Microsoft extension type `__int128` which has been there for a long time. I feel like we should have appropriate coverage already

Sounds good to me.

lgtm with the i128 test that Fznamznon suggested, and a release note is a good idea too.

https://github.com/llvm/llvm-project/pull/130993