[clang] [Clang] Accept auto parameters pre-C++20 as an extension (PR #200670)

[Corentin Jabot via cfe-commits]

cor3ntin wrote:

> Could you share what you have in mind here? for concepts you first kinda need the keywords, which we don't have pre-C++20.

Good point about not having the keyword.

Still, what does `void f(Foo auto)` do?


https://github.com/llvm/llvm-project/pull/200670