This makes Rustdoc titles for items read like
"x in cratename::blah::foo - Rust". Title for modules and other
non-items are unchanged, and still read like
"doccratenameconst::blah::foo - Rust". This makes managing several open
Rustdoc tabs easier.

Closes rust-lang#84371.

…exhaustive`

Replace all `fmt.pad` with `debug_struct`

This replaces any occurrence of:
- `f.pad("X")` with `f.debug_struct("X").finish()`
- `f.pad("X { .. }")` with `f.debug_struct("X").finish_non_exhaustive()`

This is in line with existing formatting code such as
https://github.com/rust-lang/rust/blob/125505306744a0a5bb01d62337260a95d9ff8d57/library/std/src/sync/mpsc/mod.rs#L1470-L1475

Move `sys::vxworks` code to `sys::unix`

Follow-up to rust-lang#77666, `sys::vxworks` is almost identical to `sys::unix`, the only differences are the `rand`, `thread_local_dtor`, and `process` implementation. Since `vxworks` is `target_family = unix` anyway, there is no reason for the code not to live inside of `sys::unix` like all the other unix-OSes.

https://github.com/rust-lang/rust/blob/e41f378f825488a537b024fc3ed599d9c12fda96/compiler/rustc_target/src/spec/vxworks_base.rs#L12

``@rustbot`` label: +T-libs-impl

Document that `index` and `index_mut` can panic

I thought this was noteworthy and I think a bit more explicitness does no harm.

…trochenkov

Improve the docstrings of the `Lto` struct.

This change is the result of [this zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Making.20sense.20of.20LTO.20modes.20in.20rustc).

Hopefully it makes things a little clearer. What do you think?

Fix broken doc link

…=jackh726

Add GAT related tests

Closes rust-lang#79949
Closes rust-lang#79636
Closes rust-lang#78671
Closes rust-lang#70303
Closes rust-lang#70304
Closes rust-lang#71176

Write Rustdoc titles like "x in crate::mod - Rust"

This makes Rustdoc titles for items be like "Widget in cratename::blah::foo - Rust". Titles for modules and other non-items are unchanged, and still read like "cratename::blah::foo - Rust". This makes managing several open Rustdoc tabs easier.

![A screenshot of several open Rustdoc tabs](https://user-images.githubusercontent.com/10530973/115457675-d608f180-a1f2-11eb-87a8-838a32b4e3f7.png)

This also adds some tests for the new title behavior.

Closes rust-lang#84371.

…ithout-fields-a-little-bit-less-verbose, r=kennytm

Format `Struct { .. }` on one line even with `{:#?}`.

The result of `debug_struct("A").finish_non_exhaustive()` before this change:
```
A {
    ..
}
```
And after this change:
```
A { .. }
```

If there's any fields, the result stays unchanged:
```
A {
    field: value,
    ..
}

…, r=jyn514

Support `x.py doc std --open`

I usually run this command:

```
./x.py doc std --stage 1 --jobs 8
```

Then I gave a try to `--open` and realized it wasn't working. I finally realized it was simply because it was only handling paths starting with `library`. This PR allows to handle both kinds of paths.

cc ``@jyn514``
r? ``@Mark-Simulacrum``

Remove `delete` alias from `mem::drop`.

See rust-lang#81988 (comment) and rust-lang#81988 (comment)