Add missing link for read_line

Seems I found a missing link 🔗

https://doc.rust-lang.org/stable/std/io/trait.BufRead.html#errors-2

Update .mailmap with my real name

Good morning, the Rust team!

Once upon a time I was a modest-scale contributor. Sadly, various turbulences made me step away from my participation in the project. It's great to see how far it's gone.

I would appreciate it if you accepted this small change to the .mailmap file so that it shows my real name as back then I was using an alias. If doubts arise if I am the same person, I will be happy to provide further evidence. :)

Kind regards.

Implement implied shortcut links for intra-rustdoc-links

cc https://github.com/rust-lang/rust/issues/43466

Needs https://github.com/google/pulldown-cmark/pull/126

r? @QuietMisdreavus

Mark doc examples w/ `extern` blocks as `ignore`.

Fixes https://github.com/rust-lang/rust/issues/48218.

Fix broken documentation link.

None

inform user where to give a type annotation

should resolve #47777
previous pull request https://github.com/rust-lang/rust/pull/47982 was closed because of a mistaken rebase.
r? @estebank

rustdoc: move manual "extern crate" statements outside automatic "fn main"s in doctests

Gated on https://github.com/rust-lang/rust/pull/48095 - I based the branch atop that so i could show off the change in one of its tests, the actual change in this PR is just the last commit

There are a handful of unfortunate assumptions in the way rustdoc processes `extern crate` statements in doctests:

1. In the absence of an `extern crate` statement in the test, if the test also uses the local crate name, it will automatically insert an `extern crate cratename;` statement into the test.
2. If the doctest *does* include an `extern crate` statement, rustdoc will not automatically insert one, on the assumption that doing so would introduce a duplicate import.
3. If a doctest does not have the substring `fn main` outside a comment, rustdoc will wrap the whole doctest in a generated `fn main` so it can be compiled.

In short, whenever you write a doctest like this...

```rust
//! extern crate my_crate;
//! my_crate::some_cool_thing();
```

...rustdoc will turn it into (something like) this:

```rust
fn main() {
extern crate my_crate;
my_crate::some_cool_thing();
}
```

This creates issues when compiled, because now `my_crate` isn't even properly in scope! This forces people who want to have multiple crates in their doctests (or an explicit `extern crate` statement) to also manually include their own `fn main`, so rustdoc doesn't put their imports in the wrong place.

This PR just taps into another processing step rustdoc does to doctests: Whenever you add an `#![inner_attribute]` to the beginning of a doctest, rustdoc will actually splice those out and put it before the generated `fn main`. Now, we can just do the same with `extern crate`s at the beginning, too, and get a much nicer experience.

Now, the above example will be converted into this:

```rust
extern crate my_crate;
fn main() {
my_crate::some_cool_thing();
}
```

Generate documentation for auto-trait impls

A new section is added to both both struct and trait doc pages.

On struct/enum pages, a new 'Auto Trait Implementations' section displays any synthetic implementations for auto traits. Currently, this is only done for Send and Sync.

![Auto trait implementations for Cloned](https://i.imgur.com/XtTV6IJ.png)

On trait pages, a new 'Auto Implementors' section displays all types which automatically implement the trait. Effectively, this is a list of all public types in the standard library.

![Auto trait implementors for Send](https://i.imgur.com/3GRBpTy.png)

Synthesized impls for a particular auto trait ('synthetic impls') take generic bounds into account. For example, a type
```rust
struct Foo<T>(T)
```
 will have 'impl<T> Send for Foo<T> where T: Send' generated for it.

Manual implementations of auto traits are also taken into account. If we have
the following types:

```rust
struct Foo<T>(T)
struct Wrapper<T>(Foo<T>)
unsafe impl<T> Send for Wrapper<T>' // pretend that Wrapper<T> makes this sound somehow
```

Then Wrapper will have the following impl generated:
```rust
impl<T> Send for Wrapper<T>
```
reflecting the fact that 'T: Send' need not hold for 'Wrapper<T>: Send' to hold

Lifetimes, HRTBS, and projections (e.g. '<T as Iterator>::Item') are taken into account by synthetic impls:

![A ridiculous demonstration type](https://i.imgur.com/TkZMWuN.png)

However, if a type can *never* implement a particular auto trait (e.g. `struct MyStruct<T>(*const T)`), then a negative impl will be generated (in this case, `impl<T> !Send for MyStruct<T>`)

All of this means that a user should be able to copy-paste a syntheticimpl into their code, without any observable changes in behavior (assuming the rest of the program remains unchanged).

Derive std::cmp::Reverse as Copy or Clone

If the type parameter is Copy or Clone, then `Reverse` should be too.

This removes the implicit dependency on the iteration
order of FxHashMap

Fixes https://github.com/rust-lang/rust/issues/48341

A new section is added to both both struct and trait doc pages.

On struct/enum pages, a new 'Auto Trait Implementations' section displays any
synthetic implementations for auto traits. Currently, this is only done
for Send and Sync.

On trait pages, a new 'Auto Implementors' section displays all types
which automatically implement the trait. Effectively, this is a list of
all public types in the standard library.

Synthesized impls for a particular auto trait ('synthetic impls') take
into account generic bounds. For example, a type 'struct Foo<T>(T)' will
have 'impl<T> Send for Foo<T> where T: Send' generated for it.

Manual implementations of auto traits are also taken into account. If we have
the following types:

'struct Foo<T>(T)'
'struct Wrapper<T>(Foo<T>)'
'unsafe impl<T> Send for Wrapper<T>' // pretend that Wrapper<T> makes
this sound somehow

Then Wrapper will have the following impl generated:
'impl<T> Send for Wrapper<T>'
reflecting the fact that 'T: Send' need not hold for 'Wrapper<T>: Send'
to hold

Lifetimes, HRTBS, and projections (e.g. '<T as Iterator>::Item') are
taken into account by synthetic impls

However, if a type can *never* implement a particular auto trait
(e.g. 'struct MyStruct<T>(*const T)'), then a negative impl will be
generated (in this case, 'impl<T> !Send for MyStruct<T>')

All of this means that a user should be able to copy-paste a synthetic
impl into their code, without any observable changes in behavior
(assuming the rest of the program remains unchanged).

Rollup of 6 pull requests

- Successful merges: #48194, #48273, #48274, #48275, #48282, #48312
- Failed merges:

Fixes https://github.com/rust-lang/rust/issues/48218.

Unify 'Platform-specific behavior' documentation headings.

None

Fix spelling in core::iter::repeat_with: s/not/note

Fixes spelling error in https://github.com/rust-lang/rust/pull/48156#discussion_r168718452.
Tracking issue: https://github.com/rust-lang/rust/issues/48169

fix more typos found by codespell.

Remove hoedown from rustdoc

Finally the time has come!

r? @QuietMisdreavus

Add a warning to File about mutability.

Fixes #47708.

Doc test command

r? @Mark-Simulacrum

RFC 2070 part 1: PanicInfo and Location API changes

This implements part of https://rust-lang.github.io/rfcs/2070-panic-implementation.html
Tracking issue: https://github.com/rust-lang/rust/issues/44489

* Move `std::panic::PanicInfo` and `std::panic::Location` to a new `core::panic` module. The two types and the `std` module were already `#[stable]` and stay that way, the new `core` module is `#[unstable]`.
* Add a new `PanicInfo::message(&self) -> Option<&fmt::Arguments>` method, which is `#[unstable]`.
* Implement `Display` for `PanicInfo` and `Location`

Relax termination_trait's error bound

As per [this conversation](https://github.com/withoutboats/failure/issues/130#issuecomment-358572413) with @withoutboats and @bkchr