[clang] [llvm] [Clang] Reintroduce obsolete libclang symbols to avoid an ABI break (PR #149079)

[via llvm-commits]

Sirraide wrote:

> Don't you have to undo the changes to clang/tools/libclang/libclang.map too? Else these might not be marked as exported on all platforms. (This: https://github.com/llvm/llvm-project/pull/119269/files#diff-2aa9e5e6908b0366b33796fa1f944b25d5b77abdf8eaceac7de55ccadaa7f04f)

CC @AaronBallman 

https://github.com/llvm/llvm-project/pull/149079