[clang] Add _MM_FROUND_TO_NEAREST_TIES_EVEN to avx512fintrin.h (PR #99691)

[Robin Charles Gilbert via cfe-commits]

robincharlesgilbert wrote:

To be fair, regarding MSVC, it might be more than just a chicken and the egg problem. It is sometimes in the best interests of Microsoft to make it as painful as possible for their customers to port their code onto other platforms, or to use standard libraries which are not implemented by Microsoft. On the other hand, when it comes to the rounding modes (for other functions than the intrinsics of this PR), MSVC has non-standard functions found nowhere else (e.g. _controlfp) which are using more objectionable names (_RC_CHOP for round toward zero... instead of a more natural name like _RC_ZERO).

Outside the Microsoft ecosystem, code portability is usually less of an issue. There is also less of a need to twist the hand of a patron to get the owner of a proprietary compiler to fix something.

https://github.com/llvm/llvm-project/pull/99691