[clang] [llvm] [clang] Initial frontend C-restrict support (PR #173394)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Hmm... while I suspect there is value to emitting this information, the form of it is pretty awkward.  I'd really like to see what @efriedma-quic and @rjmccall have to say, since this is part of codegen.

https://github.com/llvm/llvm-project/pull/173394