MIR borrowck: implement union-and-array-compatible semantics

Fixes #44831.
Fixes #44834.
Fixes #45537.
Fixes #45696 (by implementing DerefPure semantics, which is what we want going forward).

r? @nikomatsakis

Rollup of 7 pull requests

- Successful merges: #46136, #46378, #46431, #46483, #46495, #46502, #46512
- Failed merges:

Give compile_error macro examples

I cannot get Rust to build at all with it complaining about GCC not being a valid C compiler or something, so letting TravisCI be my tester...

Fixes #46171

Improve search style

Fixes #46494.

r? @QuietMisdreavus

Update old link

The CONTRIBUTING.md page currently links to an old wiki page in rust-lang/rust-wiki-backup. There is a more up-to-date page in-tree so I changed the link to point there so new contributors can find it more easily.

Document behavior of `ptr::swap` with overlapping regions of memory.

Fixes https://github.com/rust-lang/rust/issues/44479.

Mention the name of ? in Result's docs

Fixes #42725

or at least, this is the best we can really do. #35946 is tracking
better errors already, so that should cover the other part of it.

Fix use of rand in liballoc benches

Clarify what `-D warnings` or `-F warnings` does

They set all lints currently on the warning level to `deny` or `forbid`,
respectively.

coherence: fix is_knowable logic

A trait-ref that passes the orphan-check rules can still be implemented in a crate downstream from our crate (for example, `LocalType for LocalTrait<_>` might be matched by a `LocalType for LocalTrait<TypeFromDownstreamCrate>`), and this should be known by the `is_knowable`  logic.

Trait selection had a hackfix for this, but it's an hacky fix that does not handle all cases. This patch removes it.

fixes #43355.

r? @nikomatsakis

Needs a crater run

rustc_trans: don't write discriminants for uninhabited variants

Fixes #46519.

Patch as suggested by eddyb: https://github.com/rust-lang/rust/issues/46519#issuecomment-349443519

Update rls and rustfmt and set them testing

r? @alexcrichton

Change "Types/modules" title of search tab to be more accurate

From issue #45787. Used "In name" as per suggestion from @Seeker14491.

Fixes #46519.

Patch as suggested by eddyb:
https://github.com/rust-lang/rust/issues/46519#issuecomment-349443519

Tabs are "In Names", "In Parameters", and "In Return Types".

This fixes the tests for issue #29793

I'm not sure how correct it this, but it gets whatever needs to compile
to compile.

This improves performance on large functions.

Fixes #44831.
Fixes #44834.
Fixes #45537.
Fixes #45696 (by implementing DerefPure semantics, which is what we want
going forward).

template month/year, version into man pages while building dist tarball

![the_man](https://user-images.githubusercontent.com/1076988/33596149-963956f4-d94f-11e7-926f-e683217765e5.png)

This is meant to resolve #25689.

r? @alexcrichton

Add armv5te-unknown-linux-gnueabi to cross builder

This is the only linux target missing in the dist builders.

Fixes #42725

or at least, this is the best we can really do. #35946 is tracking
better errors already, so that should cover the other part of it.

rustc_mir: don't move temporaries that are still used later.

This should unbreak using the MIR borrow-checker on `libcore` (assuming #46268 is merged).