This is mainly to support migrating from AtomicUsize, for the strict
provenance experiment.

Fixes rust-lang#95492

Fixes a weirdly-rendered section of the std::string::String docs.

Instead of generating `#impl`, `#impl-1`, etc., generate IDs
like `#impl-Foo<M>`.

Co-authored-by: Noah Lev <camelidcamel@gmail.com>

…lnay

Allow arithmetic and certain bitwise ops on AtomicPtr

This is mainly to support migrating from `AtomicUsize`, for the strict provenance experiment.

This is a pretty dubious set of APIs, but it should be sufficient to allow code that's using `AtomicUsize` to manipulate a tagged pointer atomically. It's under a new feature gate, `#![feature(strict_provenance_atomic_ptr)]`, but I'm not sure if it needs its own tracking issue. I'm happy to make one, but it's not clear that it's needed.

I'm unsure if it needs changes in the various non-LLVM backends. Because we just cast things to integers anyway (and were already doing so), I doubt it.

API change proposal: rust-lang/libs-team#60

Fixes rust-lang#95492

…-and-impl-item, r=cjgillot

Replace some `guess_head_span` with `def_span`

This patch fixes a part of rust-lang#97417.
r? `@cjgillot`

…impl, r=GuillaumeGomez

rustdoc: filter '_ lifetimes from ty::Generics

Fixes a weirdly-rendered section of the std::string::String docs.

Before:

![image](https://user-images.githubusercontent.com/1593513/177256873-20b9cf6e-2429-4865-853b-b269d74672f4.png)

After:

![image](https://user-images.githubusercontent.com/1593513/177256900-ef3efd17-f624-40c5-af90-fe709ec034f2.png)

…, r=notriddle

rustdoc: Add more semantic information to impl IDs

Take over of rust-lang#92745.

I fixed the last remaining issue for the links in the sidebar (mentioned by `@jsha)` and fixed the few links broken in the std/core docs.

cc `@camelid`
r? `@notriddle`

Fix typo in file descriptor docs

docs: Add overview of `rustc_middle::mir::TerminatorKind`

Remove erroneous doc comment

Fixes the formatting issue shown here:

<img width="803" alt="Screen Shot 2022-07-06 at 12 50 56 PM" src="https://user-images.githubusercontent.com/19642016/177612734-2d881c6a-2850-4c1b-8f1a-08339ad5bfbc.png">