[clang] [Clang][Parser] Fix crash of clang when using C++ constructs like :: in C code (PR #74926)

[Timm Baeder via cfe-commits]

tbaederr wrote:

It doesn't need a specific approval, just _any_. And @shafik has already approved this PR, so it can now be merged.

https://github.com/llvm/llvm-project/pull/74926