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

[M. Zeeshan Siddiqui via cfe-commits]

codemzs wrote:

I am sorry for the delay. I plan to finish this PR before end of this year but can expedite it if someone needs the change sooner.

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