[clang] [clang] Support __typeof_unqual__ in all C modes (PR #87392)

[Tobias Hieta via cfe-commits]

tru wrote:

The final decision is Toms, but I don't think it qualifies since we are so late in the current process and that 19 will start in just a few months. 

https://github.com/llvm/llvm-project/pull/87392