[clang] [clang] Emit diagnostic for typedef+auto missed case in C++98/pre-C23 C (PR #210141)

[via cfe-commits]

rahulana-quic wrote:

> I would like to see a test case for the pre-C23 behavior.

I jumped the gun a little and added code to handle some extra cases. Pre-C23 was not broken before and that behavior is left unchanged.

https://github.com/llvm/llvm-project/pull/210141