Allow `!` as the return type of proc/closure literals

Fixes #13490.
Change rustc to say `array` instead of `vector`
core: Make TwoWaySearcher reset its prefix memory when shifting by byteset

Closes #16878.
Add many comments to TwoWaySearcher.
Add some tests for closures that return `!`
Add unnecessary_import_braces lint.

The lint checks any unnecessary braces around one imported item like
`use std::num::{abs};`.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Separate static item recursion check into its own pass

This new pass is run before type checking so that recursive items
are detected beforehand.  This prevents going into an infinite
recursion during type checking when a recursive item is used in
an array type.

As a bonus, use `span_err` instead of `span_fatal` so multiple
errors can be reported.

Closes issue #17252
Add regression test for issue #17252
json: Properly handle trailing comma error in object decoding.

Closes #16945
Don't use 'here'

Fixes #17225
properly annotate C code in the guide

Without 'notrust,' we were getting a playpen link.

Fixes #17228.
remove references to HM inference

Fixes #17229.
remove rendundant function

Fixes #17230.
use _sample configurations..._ rather than _here_ as link text
Add missing unused variable warnings for for loop bindings
add missing semicolon to fix configure on darwin
mk: Update how the build deals with version labels. #16677

Adds a new configure flag, --release-channel, which determines how the version
number should be augmented with a release label, as well as how the distribution
artifacts will be named. This is entirely for use by the build automation.

--release-channel can be either 'source', 'nightly', 'beta', or 'stable'.

Here's a summary of the affect of these values on version number and
artifact naming, respectively:

* source - '0.12.0-pre', 'rust-0.12.0-pre-...'
* nightly - '0.12.0-nightly', 'rust-nightly-...'
* beta - '0.12.0-beta', 'rust-beta-...'
* stable - '0.12.0', 'rust-0.12.0-...'

Per http://discuss.rust-lang.org/t/rfc-impending-changes-to-the-release-process/508/1
stop spawning so many tasks in guide-tasks

1000 tasks * 2MiB stack size -> 2GiB of virtual memory

On a 64-bit OS, a 32-bit executable has 4GiB available, but the kernel
gets half of the available address space so the limit is 2GiB on 32-bit.

Closes #17044
Correct windows install link in guide

This closes #17260. The guide references the old install location for
the windows rust install before it was split into 64bit and 32bit
installers. This adds a link to each binary.
Rename std::io::net::unix to std::io::net::pipe.

Renamed as we may support pipes for other platforms.

Closes #12093

[breaking-change]