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

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

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.

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