Currently fails to build:

    error[E0600]: cannot apply unary operator `!` to type `!`
       --> library/core/tests/ops.rs:239:8
        |
    239 |     if !return () {}
        |        ^^^^^^^^^^ cannot apply unary operator `!`

Fix rust-lang#93074

They don't need to be `pub`. Making them crate-private improves code
clarity and `dead_code` linting.

… doc

Stabilize arc_new_cyclic

This stabilizes feature `arc_new_cyclic` as the implementation has been merged for one year and there is no unresolved questions. The FCP is not started yet.

Closes rust-lang#75861 .

``@rustbot`` label +T-libs-api

impl Not for !

The lack of this impl caused trouble for me in some degenerate cases of macro-generated code of the form `if !$cond {...}`, even without `feature(never_type)` on a stable compiler. Namely if `$cond` contains a `return` or `break` or similar diverging expression, which would otherwise be perfectly legal in boolean position, the code previously failed to compile with:

```console
error[E0600]: cannot apply unary operator `!` to type `!`
   --> library/core/tests/ops.rs:239:8
    |
239 |     if !return () {}
    |        ^^^^^^^^^^ cannot apply unary operator `!`
```

Fix spacing for `·` between stability and source

This puts in an actual space (by adjusting the space-eating operators in our templates), updates the test, and remove the now-unnecessary CSS rule.

r? ``@GuillaumeGomez``

Tweak `expr.await` desugaring `Span`

Fix rust-lang#93074

Unify search input and buttons size

Fixes rust-lang#93060.

Here what it looks like:

![Screenshot from 2022-01-20 21-38-19](https://user-images.githubusercontent.com/3050060/150418571-fefd6538-b3ee-4dd2-b77b-77e96bcfa0ed.png)
![Screenshot from 2022-01-20 21-38-22](https://user-images.githubusercontent.com/3050060/150418570-53ba259b-9bd4-4084-8b43-d74a5752d712.png)

You can test it [here](https://rustdoc.crud.net/imperio/unify-sizes/std/index.html).

r? ``@jsha``

update uclibc instructions for new toolchain, add link from platforms doc

2 quick things:
1) `libc` was updated to make use of features in a uclibc version more recent than the recommended toolchain in the target document, so I updated the link.
2) As has been done with other platforms, link directly from the platform support doc to the target-specific document.

…omez

rustdoc: Make some `pub` items crate-private

They don't need to be `pub`. Making them crate-private improves code
clarity and `dead_code` linting.

…de, r=Mark-Simulacrum

Remove dead code from build_helper

Tested with `./x.py check` ran on x86_64 Linux.