Fix some punctuation and wording, and add intra-documentation links.

Fixes: rust-lang#80060

Also adds additional test cases for coverage of doctests.

This fixes a mobile UI bug where a vertical scrollbar would always be
rendered on the sidebar nav when the menu was closed.

Co-authored-by: Joshua Nelson <[email protected]>

Change:
```
`parse` can parse any type that...
```
to:
```
`parse` can parse into any type that...
```
Word `into` added to be more precise and in coherence with other parts of the doc.

…ntifier-E0435, r=petrochenkov

Add pointing const identifier when emitting E0435

Fix rust-lang#79919

…4.0, r=wesleywiser

MIR Inline is incompatible with coverage

Fixes: rust-lang#80060

Fixed by disabling inlining if `-Zinstrument-coverage` is set.

The PR also adds additional use cases to the coverage test for doctests.

r? `@wesleywiser`
cc: `@tmandry`

Edit rustc_ast::tokenstream docs

Fix some punctuation and wording, and add intra-documentation links.

Properly handle primitive disambiguators in rustdoc

Fixes rust-lang#80559

r? ``@jyn514``

Is there a way to test that the generated intra-doc link is what I expect?

Remove bottom margin from crate version when the docs sidebar is collapsed

This fixes a mobile UI bug where a vertical scrollbar would always be
rendered on the sidebar nav when the menu was closed.  When opened, the overflow would be handled by the opened sidebar, causing the scrollbar to disappear, and the contents to shift to the right.

## Firefox
**Before**
![before-ff](https://user-images.githubusercontent.com/139487/103713599-c2f74c00-4f8a-11eb-88c0-d5c6c088f8a0.png)
![before](https://user-images.githubusercontent.com/139487/103713793-2bdec400-4f8b-11eb-8223-94b77cc05f71.gif)

**After**
![after-ff](https://user-images.githubusercontent.com/139487/103713605-c8ed2d00-4f8a-11eb-9ee8-f86cafaa8775.png)
![after](https://user-images.githubusercontent.com/139487/103713805-31d4a500-4f8b-11eb-9e5b-4156402ca43e.gif)

## Chrome
**Before**
![localhost_8000_unicode_xid_ (1)](https://user-images.githubusercontent.com/139487/103713626-d60a1c00-4f8a-11eb-8605-cc98e04e9ad0.png)

**After**
![localhost_8000_unicode_xid_](https://user-images.githubusercontent.com/139487/103713622-d1456800-4f8a-11eb-8c66-7d19f81614ca.png)

rustdoc: Turn `next_def_id` comments into docs

Split out from rust-lang#80740.

r? ``@jyn514``

…=lzutao

Don't use to_string on Symbol in rustc_passes/check_attr.rs

Improve code from rust-lang#80686.

r? ``@lzutao``

Improve wording of parse doc

Change:
```
`parse` can parse any type that...
```
to:
```
`parse` can parse into any type that...
```
Word `into` added to be more precise and in coherence with other parts of the doc.

Return EOF_CHAR constant instead of magic char.

rustc_parse: Better spans for synthesized token streams

I think using the nonterminal span for synthesizing its tokens is a better approximation than using `DUMMY_SP` or the attribute span like rust-lang#79472 did in `expand.rs`.

r? `@Aaron1011`