Fixes rust-lang#67593

`ptr` of `slice::Iter` and `slice::IterMut` can never be null, but this
fact wasn't exploited for layout optimizations. By changing `ptr` from
`*<mutability> T` to `NonNull<T>`, the compiler can now optimize layout
of `Option<Iter<'a, T>>`.

Fixes rust-lang#65721

FCP: rust-lang#65721 (comment)

add IntoFuture trait and support for await

The [async-await RFC](https://rust-lang.github.io/rfcs/2394-async_await.html#the-await-compiler-built-in) mentions being able to `await` anything implementing `IntoFuture`. Somewhere along the way, it was left out.

reuse `capacity` variable in slice::repeat

None

Use NonNull in slice::Iter and slice::IterMut.

`ptr` of `slice::Iter` and `slice::IterMut` can never be null, but this
fact wasn't exploited for layout optimizations. By changing `ptr` from
`*<mutability> T` to `NonNull<T>`, the compiler can now optimize layout
of `Option<Iter<'a, T>>`.

Closes rust-lang#67228

Update libc to 0.2.66

cc @gnzlbg @alexcrichton

…-intrinsics, r=Centril

Use issue = "none" instead of "0" in intrinsics

`issue = "0"` was incorrectly used in rust-lang@9ee16e1, the project is moving away from issue 0

…r=RalfJung

Add Scalar::to_(u|i)16 methods

r? @RalfJung

…docs, r=Dylan-DPC

Remove `compiler_builtins_lib` documentation

Fixes rust-lang#67593

…r=oli-obk

Use the correct type for static qualifs

Closes rust-lang#67609

…r=steveklabnik

Remove redundant link texts

Most of these links are followed by a parenthesized expression.  I think that the redundant link texts were added to prevent interpretation as an inline link.  This is unnecessary since the closing square bracket and opening parenthesis are separated by whitespace.

…nks, r=steveklabnik

Convert collapsed to shortcut reference links

…ulacrum

Update .mailmap

…dtolnay

Document safety of Path casting

I would personally feel more comfortable making the relevant (internal anyway) types repr(transparent) and then documenting that we can make these casts because of that, but I believe this is a more minimal PR, so posting it first.

Resolves rust-lang#45910.

…ion-test, r=Centril

Add regression test for old NLL ICE

This fails on nightly-2018-06-24.

Resolves rust-lang#51770

Stabilize the `matches!` macro

Fixes rust-lang#65721

FCP: rust-lang#65721 (comment)

…mulacrum

Fix some mailmap entries

r? @pietroalbini