[clang] Reject invalid integer constants in unevaluated preprocessor operands (PR #134884)

[Richard Smith via cfe-commits]

https://github.com/zygoloid approved this pull request.

LGTM.

I suppose if people complain, we can make the non-live value case a warning rather than an error, but given no other implementation does, I think it makes sense not to do that speculatively.

https://github.com/llvm/llvm-project/pull/134884