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

[Joshua Cranmer via cfe-commits]

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

I haven't attempted to make my way through the sema changes yet, but some comments already:

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