[clang] [clang-cl] Fix value of __FUNCTION__ and __FUNC__ in MSVC mode for c++. (PR #66120)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

I've reverted the changes in 9243b1bfdbf4c8b8f3f8c8e45b57f784311adaac, but you should handle the revert yourself next time because you have commit privileges and it's possible the person requesting a revert does not. (If you can't do the revert immediately for whatever reason, it's fine to tell people something along the lines of "I'll revert by <time> unless someone else is able to revert it sooner.")

https://github.com/llvm/llvm-project/pull/66120