[llvm] [Utils][vim] Match more hexadecimal float constants (PR #99000)

[Andrzej Warzyński via llvm-commits]

https://github.com/banach-space approved this pull request.

Thanks, LGTM!

I guess this intends to match https://llvm.org/docs/LangRef.html#simple-constants? 

https://github.com/llvm/llvm-project/pull/99000