constraints:

- clean/inline.rs needs this map to fill in traits when inlining
- fold.rs needs this map to allow passes to fold trait items
- html/render.rs needs this map to seed the Cache.traits map of all
  known traits

The first two are the real problem, since `DocFolder` only operates on
`clean::Crate` but `clean/inline.rs` only sees the `DocContext`. The
introduction of early passes means that these two now exist at the same
time, so they need to share ownership of the map. Even better, the use
of `Crate` in a rustc thread pool means that it needs to be Sync, so it
can't use `Lrc<Lock>` to manually activate thread-safety.

`parking_lot` is reused from elsewhere in the tree to allow use of its
`ReentrantMutex`, as the relevant parts of rustdoc are still
single-threaded and this allows for easier use in that context.

those get handled properly in strip-hidden anyway

Remove usages of span_suggestion without Applicability

Use `Applicability::Unspecified` for all of them instead.

Shall deprecations for the non-`_with_applicability` functions be added?

Shall clippy be addressed somehow?

r? @estebank

Update some `*-sys` dependencies of Cargo/RLS

This is intended to help solve #54206 on nightly where the RLS on MinGW is
having build issues with accidentally building a `curl` library which links to
pthread symbols on Windows (where it should use native mutex locking instead).
The build system for these `*-sys` crates have all been rewritten to be based on
`cc` to bypass native build systems and platform detection to make sure we
configure them correctly.

This is intended to help solve #54206 on nightly where the RLS on MinGW is
having build issues with accidentally building a `curl` library which links to
pthread symbols on Windows (where it should use native mutex locking instead).
The build system for these `*-sys` crates have all been rewritten to be based on
`cc` to bypass native build systems and platform detection to make sure we
configure them correctly.

Split `Liveness::users` into three.

This reduces memory usage on some benchmarks because no space is wasted
for padding. For a `check-clean` build of `keccak` it reduces `max-rss`
by 20%.

r? @nikomatsakis, but I want to do a perf run. Locally, I had these results:
- instructions: slight regression
- max-rss: big win on "Clean" builds
- faults: big win on "Clean" and "Nll" builds
- wall-time: small win on "Clean" and "Nll" builds

So I want to see how a different machine compares.

Fix `thread` `park`/`unpark` synchronization

Previously the code below would not be guaranteed to exit when the
second unpark took the `return, // already unparked` path because there
was no write to synchronize with a read in `park`.

EDIT: doesn't actually require third thread
```
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread::{current, spawn, park};

static FLAG: AtomicBool = AtomicBool::new(false);

fn main() {
    let thread_0 = current();
    spawn(move || {
        thread_0.unpark();
        FLAG.store(true, Ordering::Relaxed);
        thread_0.unpark();
    });

    while !FLAG.load(Ordering::Relaxed) {
        park();
    }
}
```

I have some other ideas on how to improve the performance of `park` and `unpark` using fences, avoiding any atomic RMW when the state is already `NOTIFIED`, and also how to avoid calling `notify_one` without the mutex locked. But I need to write some micro benchmarks first, so I'll submit those changes at a later date if they prove to be faster.

Fixes https://github.com/rust-lang/rust/issues/53366 I hope.

Fix camel case type warning for types with trailing underscores

Fixes #54099

Update to a new pinning API.

~~Blocked on #53843 because of method resolution problems with new pin type.~~

@r? @cramertj

cc @RalfJung @pythonesque anyone interested in #49150

Use `HybridBitSet` in `SparseBitMatrix`.

This fixes most of the remaining NLL memory regression.

r? @pnkfelix, because you reviewed #54286.
cc @nikomatsakis, because NLL
cc @Mark-Simulacrum, because this removes `array_vec.rs`
cc @lqd, because this massively improves `unic-ucd-name`, and probably other public crates

NLL: Deduplicate errors for incorrect move in loop

Fixes #53807.

r? @nikomatsakis

By introducing a new map that tracks the errors reported and the
`Place`s that spawned those errors against the move out that the error
was referring to, we are able to silence duplicate errors by emitting
only the error which corresponds to the most specific `Place` (that which
other `Place`s which reported errors are prefixes of).

This generally is an improvement, however there is a case -
`liveness-move-in-while` - where the output regresses.

This is useful in debugging when and where errors are emitted in
logs.

Add feature to enable bind by move pattern guards

Implement #15287 as described on https://github.com/rust-lang/rust/issues/15287#issuecomment-404827419

Rollup of 9 pull requests

Successful merges:

 - #53522 (Add doc for impl From for Addr)
 - #54097 (rustdoc: Remove namespace for keywords)
 - #54205 (Add treat-err-as-bug flag in rustdoc)
 - #54225 (Regression test for rust-lang/rust#53675.)
 - #54232 (add `-Z dont-buffer-diagnostics`)
 - #54273 (Suggest to change numeric literal instead of casting)
 - #54299 (Issue 54246)
 - #54311 (Remove README with now-out-of-date docs about docs.)
 - #54313 (OsStr: Document that it's not NUL terminated)

Failed merges:

r? @ghost

OsStr: Document that it's not NUL terminated

I somehow got confused into thinking this was the case, but
it's definitely not.  Let's help the common case of people who
have an `OsStr` and need to call e.g. Unix APIs.

Remove README with now-out-of-date docs about docs.

These docs haven't really been touched in years, and from what I tried, the `rustdoc` commands don't work. Seems like we don't need this?

Issue 54246

I added the option of providing a help message for deprecated features, that takes precedence over the default `help: remove this attribute` message, along with messages for the features that mention replacements in the reason for deprecation.

Fixes #54246.