[clang] [llvm] [Clang][C++23] Core language changes from P1467R9 extended floating-point types and standard names. (PR #78503)

[Joshua Cranmer via llvm-commits]

https://github.com/jcranmer-intel commented:

I think this concludes my full look at this PR. I don't fully have a grasp on the mechanisms of C++ overload to comment on key parts of this patch.

This also doesn't implement enough of the hard cases of P1467R9 (namely _Float32/_Float64) for me to rely on correct test results to indicate that it implements the changes correctly.

https://github.com/llvm/llvm-project/pull/78503