[clang] [C23] Add INFINITY and NAN macros to <float.h> (PR #96659)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> We already have `-Wnan-infinity-disabled`, which I think is sufficient on the warning side? Haven't checked carefully to see what cases it covers.

Not this one. :-D https://godbolt.org/z/hq8jvse9o But yeah, that may be a good diagnostic to consider putting this under, but I think that diagnostic should be enabled by default when passing -Wfinite-math-only or other flags that disable infinity or nan support.

https://github.com/llvm/llvm-project/pull/96659