librustc: Allow coercions through arrays.
Vim syntax file types and traits cleanup
relicense shootout-mandelbrot.rs

Part of #14248

Main authors:
- @Ryman: OK
- @TeXitoi: OK
- @pcwalton: OK

Minor authors:
- @brson: OK
- @alexcrichton: OK
- @kballard: OK

Remark: @tedhorst was a main contributor, but its contribution
disapear with @pcwalton rewrite at af4ea11
Re-arrange TOC.

I'm going to move testing to be right AFTER the guessing game. I wanted it
to be borderline TDD, but I think that, since the first example is just one
file, it might be a bit overkill.

I'm doing this in its own commit to hopefully avoid merge conflicts.
auto merge of #15292 : alxgnon/rust/vim_syntax_cleanup, r=cmr

- Fix a couple mistakes:
  - `Ordering` is an enum, not a trait.
  - `Container` is now named `Collection`.
  - Add missing `CheckedDiv`.
  - Remove obsolete `OwnedVector`.
- Reorganize some lines to match [prelude's arrangement](http://doc.rust-lang.org/std/prelude/#reexports), making mistakes easier to spot in the future.
auto merge of #15295 : TeXitoi/rust/relicense-shootout-mandelbrot, r=brson

Part of #14248

Main authors:
- @Ryman: OK
- @TeXitoi: OK
- @pcwalton: OK

Minor authors:
- @brson: OK
- @alexcrichton: OK
- @kballard: OK

Remark: @tedhorst was a main contributor, but its contribution
disapear with @pcwalton rewrite at af4ea11

@brson OK?
Guide: variable bindings.

Whew! Who knew there was so much to say about variables.

We probably want to move the guessing game to the rust-lang org, rather than
just having it on my GitHub. Or, I could put the code inline. I think it'd be
neat to have it as a project, so people can pull it down with Cargo. Until we
make that decision, I'll just leave this here.
auto merge of #15229 : steveklabnik/rust/if, r=cmr

Whew. So much here! Feedback very welcome.

This is the first part where we actually start learning things. I'd like to think I struck a good balance of explaining enough details, without getting too bogged down, and without being confusing... but of course I'd think that. :wink: 

As I mention in the commit comment, We probably want to move the guessing game to the rust-lang org, rather than just having it on my GitHub. Or, I could put the code inline. I think it'd be neat to have it as a project, so people can pull it down with Cargo. Until we make that decision, I'll just leave this here.
auto merge of #15069 : luqmana/rust/cia, r=pcwalton

Fixes #11205.