[clang] [Clang][docs][test] Add N3517, N3652, and N3715 according to N3783 (PR #185566)

[Aaron Ballman via cfe-commits]

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

Thank you for catching these! As we get closer to C2y being finalized, I plan to do a lot more double-checking of this when we get to CD ballot comment time since I'll already have to be looking at my notes, editor's reports, and the working draft to ensure everything was applied correctly.

https://github.com/llvm/llvm-project/pull/185566