[clang] [PAuth] Use different discriminators for __int128_t / __uint128_t / _BitInt(n) (PR #140276)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

This looks reasonable to me, but are we able to add a flag on it - we might need to be able to disable it on Darwin as it's technically an ABI change

https://github.com/llvm/llvm-project/pull/140276