[clang] [clang] Constant evaluation support for `__builtin_fmax{,f,l}` and `__builtin_fmin{,f,l}` (PR #225824)

[A. Jiang via cfe-commits]

frederick-vs-ja wrote:

> > The current PR title seems incorrect to me.
> 
> Why? Should it be `fmax{,f,l}` etc?

IMO yes the title should mention `fmax{,f,l}` etc. instead, since `__builtin_fmax` and `fmax` are technically different things.

https://github.com/llvm/llvm-project/pull/225824