Fix typos in atomic compare_exchange.

Failure ordering can't be Release, not (not) Acquire. Seems like a typo copy-pasted all over.

Reinstate fast_reject for overlap checking

The initial implementation of specialization did not use the
`fast_reject` mechanism when checking for overlap, which caused a
serious performance regression in some cases.

This commit modifies the specialization graph to use simplified types
for fast rejection when possible, and along the way refactors the logic
for building the specialization graph.

Closes #32499

r? @nikomatsakis

Fix infinite loop in Arc::downgrade

Specialize equality for [T] and comparison for [u8] to use memcmp when possible

Specialize equality for [T] and comparison for [u8] to use memcmp when possible

Where T is a type that can be compared for equality bytewise, we can use
memcmp. We can also use memcmp for PartialOrd, Ord for [u8].

Use specialization to call memcmp in PartialEq for slices for certain element types. This PR does not change the user visible API since the implementation uses an intermediate trait. See commit messages for more information.

The memcmp signature was changed from `*const i8` to `*const u8` which is in line with how the memcmp function is defined in C (taking const void * arguments, interpreting the values as unsigned bytes for purposes of the comparison).

Lay groundwork for RFC 1422  and improve `PrivateItemsInPublicInterfacesVisitor`

This PR lays groundwork for RFC 1422 (cc #32409) and improves `PrivateItemsInPublicInterfacesVisitor`. More specifically, it
 - Refactors away `hir::Visibility::inherit_from`, the semantics of which are obsolete.
 - Makes `hir::Visibility` non-`Copy` so that we will be able to add new variants to represent `pub(restricted)` (for example, `Visibility::Restricted(Path)`).
 - Adds a new `Copy` type `ty::Visibility` that represents a visibility value, i.e. a characterization of where an item is accessible. This is able to represent `pub(restricted)` visibilities.
 - Improves `PrivateItemsInPublicInterfacesVisitor` so that it checks for items in an interface that are less visible than the interface. This fixes #30079 but doesn't change any other behavior.

r? @nikomatsakis

Suggest adding a where-clause when that can help

Suggest adding a where-clause when there is an unmet trait-bound that can be satisfied if some type can implement it.

r? @nikomatsakis

Fix LLVM assert when handling bad intrinsic monomorphizations

Passing an invalid type to certain intrinsics would trigger an LLVM assert even though the invalid type was caught by the compiler.

r? @EddyB

in `typeck` and in `privacy::PrivacyVisitor`.

Add --extend-css option to rustdoc

Fixes #32223

r? @brson

Rollup of 12 pull requests

- Successful merges: #31762, #32538, #32634, #32668, #32679, #32691, #32724, #32727, #32744, #32761, #32766, #32774
- Failed merges:

Add `Copy` to the traits that are automatically implemented for tuples

change constant patterns to have a warning cycle

This was the original intention :(

r? @EddyB

avoid "==" in assert! when one of the values is a bool

Is suspect this is something of an idiom

Add example doc for ToOwned trait

Fixes #29342.

r? @steveklabnik

minor: update old comments

No more lifetimes in function types after https://github.com/rust-lang/rust/commit/f945190e6352a1bc965a117569532643319b400f

Remove outdated comment

The corresponding code was removed in #31824. Also remove code duplication and rename the function.

Indicate `None` is code-like in doc comment.

Remove error description of `move`

(1) `x` can be used in main() after the call to spawn(). Because the variables follow normal move semantics, though the keyword `move` is used, and i32 implements `Copy`.
(2) I remove this sentence because the previous sentence gives the referrence to `move closures`, and more description of `move` may be redundant.

Address FIXMEs related to short lifetimes in `HashMap`.

None

Minor doc fixes in "Crates and Modules" and "Lifetimes" chapters

These commits fix a couple of (minor) issues in the _Crates and Modules_ and the _Lifetimes_ chapters of the book.

r? @steveklabnik

Mention that it's not actually a data race

The example can't cause a data race since different indices are accesed.

(perhaps we should use an example where i iterates twice?)

r? @steveklabnik

doc: there is no case that is shown, so something was likely missing …

…from the change

Batch up all plugin breaking changes

https://github.com/rust-lang/rust/pull/32688 already landed so we should get this into the same nightly.

cc https://github.com/rust-lang/rust/issues/31645

 r? @nikomatsakis

Conflicts:
	src/librustc_save_analysis/lib.rs
	src/libsyntax/ast_util.rs

 The AST part of https://github.com/rust-lang/rust/pull/31937

Unlike HIR, AST still uses `Option` for field names because parser can't know field indexes reliably due to constructions like
```
struct S(#[cfg(false)] u8, u8); // The index of the second field changes from 1 during parsing to 0 after expansion.
```
and I wouldn't like to put the burden of renaming fields on expansion passes and syntax extensions.

plugin-[breaking-change] cc https://github.com/rust-lang/rust/issues/31645
r? @Manishearth

This should avoid the trait impls showing up in rustdoc.

This was the original intention :(