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

[Hans Wennborg via cfe-commits]

https://github.com/zmodem commented:

> Take the opportunity to tighten up the code slightly by ensuring that we do not access out-of-bounds characters when lexing the token.

That's a nice touch :-)

Do we already have tests somewhere checking that we can codegen this, or do we need to add that?

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