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

[via cfe-commits]

https://github.com/cor3ntin commented:

Thanks for working on this.
I made a few comments (my review is a bit shallow as floating point isn't really my area of expertise...)

Can you add 
 - Tests to check template arguments deduction works properly
 - Tests that check the behavior on platforms that do not support these types

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