[clang] [C23] Implement WG14 N3037 (PR #132939)

[Martin Uecker via cfe-commits]

uecker wrote:

Another comment about attributes: Attributes should not generally affect type compatibility (in general, but also relevant for this feature) for two reasons: 1. Standard attributes are ignorable, and this would then break. 2. Compatibility affects aliasing, one one certainly does not want to affect aliasing decisions by  adding [[deprecated]] somwhere. 
So only for vendor attributes that affect ABI, this should (and must) be considered.

https://github.com/llvm/llvm-project/pull/132939