impl Debug for SplitWhitespace.

This one got missed because `libstd_unicode` doesn't have a `deny(missing_debug_implementations)` like `libstd` and `libcore`. I think that perhaps this lint should check for items exported from other crates too.

Minor documentation improvements for StmtKind

Documentation for Semi and Marco StmtKinds.

Wasn't obvious to me what these were when writing a lint recently.

Add test for #33185

Closes #33185

Add test for #35676

Closes #35676

Add full git commit hash to release channel manifests

The full hash is necessary to build the download URL for "alternate" compiler builds. This is a first step for https://github.com/rust-lang-nursery/rustup.rs/issues/1099.

update unimplemented! docs

For #42628 (updating docs from changes from #42155).

Initial changes made to make `unimplemented!` doc comments look more like `unreachable!` and remove statement about the panic message.

r? @steveklabnik

Add clamp functions

Implementation of clamp feature:

Tracking issue: https://github.com/rust-lang/rust/issues/44095
RFC: https://github.com/rust-lang/rfcs/pull/1961

use gcc::Build rather than deprecated gcc::Config

I did `cargo update -p gcc` to upgrade only this package. Is there further process that should be follwoed when updating a build dependency from crates.io?

r? @alexcrichton
Fixes #43973

rustdoc: add new "Implementations on Foreign Types" section to traits

Demo screenshot:

![image](https://user-images.githubusercontent.com/5217170/29281219-c547f758-80e3-11e7-808f-49f592c65c5b.png)

Full demo available at https://tonberry.quietmisdreavus.net/foreign-test/foreign_test/trait.CheckIt.html

This PR splits the "Implementors" section on trait pages into two: First, for impls on types local to the crate, their impls are kept as-is, printing one line for the impl line, and any additional lines for associated types. However, for types external to the crate, they are now pulled up over the others and are printed (almost) like the summary impl on the type page itself. This gives any doc comments on these impls or methods to be exposed in the documentation.

There's just one small problem, though: [libstd docs apparently surface impls for libc and rand, possibly among others](https://tonberry.quietmisdreavus.net/foreign-std/std/marker/trait.Copy.html#foreign-impls). This adds this section to pages in the std docs where we might not want them to show up in the first place. I think this is a bug distinct from this PR, but it does make it drastically apparent.

~~My question, then, is this: Do we want this here? Taking it out involves fixing which impls are visible to rustdoc, possibly specifically when rendering the std facade. I'm convinced this is fine to land as-is, since it adds a feature specifically for non-std crates (i'm thinking of things like `num` or related crates that implement things on primitives or std types as part of their functionality).~~ (EDIT: I have an open PR to fix this: https://github.com/rust-lang/rust/pull/44026)

Add hints when intercrate ambiguity causes overlap.

I'm going to tackle #23980.

# Examples

## Trait impl overlap caused by possible downstream impl

```rust
trait Foo<X> {}
trait Bar<X> {}
impl<X, T> Foo<X> for T where T: Bar<X> {}
impl<X> Foo<X> for i32 {}

fn main() {}
```

```
error[E0119]: conflicting implementations of trait `Foo<_>` for type `i32`:
 --> test1.rs:4:1
  |
3 | impl<X, T> Foo<X> for T where T: Bar<X> {}
  | ------------------------------------------ first implementation here
4 | impl<X> Foo<X> for i32 {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
  |
  = note: downstream crates may implement Bar

error: aborting due to previous error
```

## Trait impl overlap caused by possible upstream update

```rust
trait Foo {}
impl<T> Foo for T where T: ::std::fmt::Octal {}
impl Foo for () {}

fn main() {}
```

```
error[E0119]: conflicting implementations of trait `Foo` for type `()`:
 --> test2.rs:3:1
  |
2 | impl<T> Foo for T where T: ::std::fmt::Octal {}
  | ----------------------------------------------- first implementation here
3 | impl Foo for () {}
  | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `()`
  |
  = note: upstream crates may add new impl for std::fmt::Octal in future versions

error: aborting due to previous error
```

## Inherent impl overlap caused by possible downstream impl

```rust
trait Bar<X> {}

struct A<T, X>(T, X);
impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} }
impl<X> A<i32, X> { fn f(&self) {} }

fn main() {}
```

```
error[E0592]: duplicate definitions with name `f`
 --> test3.rs:4:38
  |
4 | impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} }
  |                                      ^^^^^^^^^^^^^^ duplicate definitions for `f`
5 | impl<X> A<i32, X> { fn f(&self) {} }
  |                     -------------- other definition for `f`
  |
  = note: downstream crates may implement Bar

error: aborting due to previous error
```

## Inherent impl overlap caused by possible upstream update

```rust
struct A<T>(T);

impl<T> A<T> where T: ::std::fmt::Octal { fn f(&self) {} }
impl A<()> { fn f(&self) {} }

fn main() {}
```

```
error[E0592]: duplicate definitions with name `f`
 --> test4.rs:3:43
  |
3 | impl<T> A<T> where T: ::std::fmt::Octal { fn f(&self) {} }
  |                                           ^^^^^^^^^^^^^^ duplicate definitions for `f`
4 | impl A<()> { fn f(&self) {} }
  |              -------------- other definition for `f`
  |
  = note: upstream crates may add new impl for std::fmt::Octal in future versions

error: aborting due to previous error
```

At the moment it is always missing for Cargo and RLS.
Their respective build systems need to be modified to include
`git-commit-hash` files in their "dist" tarballs.

[MIR] Restrict ProjectionElem::Index and Storage{Live,Dead} to Local.

(see #44285)

r? @nikomatsakis

Produce expansion info for more builtin macros

r? @jseyfried

fixes #43268

Compact display of static lib dependencies

Fixes #33173

Instead of displaying one dependency per line, I've changed the format to display them all in one line.

As a bonus they're in format of linker flags (`-lfoo`), so the output can be copy&pasted if one is actually going to link as suggested.

… instead of writing an empty file.

expand on using rustup custom toolchains in CONTRIBUTING.md

fixes #42484

Should i include more notes about how to use a local build *without* rustup? It can kinda feel like a cop-out otherwise. Other means that come to mind are setting `$RUSTC` directly and fully installing it.

cc @rust-lang/docs

Resync clippy to v0.0.156

None

rustbuild: Remove invalid doctest from bootstrap.py

add test for not optimized `pow` with constant power

Closes #34947

stabilize mem::discriminant (closes #24263)