make rustdoc more responsive

* move some sidebar contents to a title bar when small
* inline description toggle when small
* make out-of-band and in-band content share space, rather than float and clash
* compress wording of out-of-band content to avoid line-wrap as much as possible
windows: Fix several tests on 64-bit.

Signed-off-by: Peter Atashian <retep998@gmail.com>
Use system rustc if configured with --enable-local-rust

This commit makes the configuration system autodetect a rustc that
is already installed and use that instead of downloading a snapshot.
fix grammar in Vec.retain's doc comment
Fix typo
Guide: strings
windows: Fix INVALID_HANDLE_VALUE
Made INVALID_HANDLE_VALUE actually a HANDLE.
Removed all useless casts during INVALID_HANDLE_VALUE comparisons.

Signed-off-by: Peter Atashian <retep998@gmail.com>
auto merge of #16321 : gioele/rust/use-local-rust, r=brson

This commit makes the configuration system autodetect a `rustc` that
is already installed and use that instead of downloading a snapshot.
auto merge of #16325 : froydnj/rust/vec-grammar-fix, r=alexcrichton

Just a small typo noticed while reading through documentation.
Register new snapshot 12e0f72
auto merge of #16349 : nikomatsakis/rust/snapshot-20140808, r=nikomatsakis
auto merge of #16327 : mdinger/rust/typo, r=steveklabnik

Fix typo. It's possible it's `These modules` but I think it's supposed to be singular because it's not refering to nested modules.
Guide: method syntax
auto merge of #16255 : steveklabnik/rust/guide_methods, r=nikomatsakis

Shifting some things around here, as I think this is a better order.
auto merge of #16333 : steveklabnik/rust/guide_strings, r=brson

I _think_ this is the right place to introduce strings. It's a bit hard to talk about without understanding pointers and ownership, but you need to have some idea of what's going on...
auto merge of #16336 : retep998/rust/master, r=brson

Several of the tests in `make check-fast` were failing so this fixes those tests.
auto merge of #16277 : Gankro/rust/responsive-docs, r=cmr

* move some sidebar contents to a title bar when small
* inline description toggle when small
* make out-of-band and in-band content share space, rather than float and clash
* compress wording of out-of-band content to avoid line-wrap as much as possible

## [Live Version Here](http://cg.scs.carleton.ca/~abeinges/doc/index.html)

Pages Of Interest:
* [Vec](http://cg.scs.carleton.ca/~abeinges/doc/std/vec/struct.Vec.html) (small path)
* [TreeSet](http://cg.scs.carleton.ca/~abeinges/doc/collections/treemap/struct.TreeSet.html) (long path)
* [std](http://cg.scs.carleton.ca/~abeinges/doc/std/index.html) (for stability dash)

TBD in a future PR is to convert links in the sidebar into a series of nest ul/li's, so that they can easily be moved to a drop-down in the new title bar. I think this is out of scope for this PR, but am willing to implement it now if desired.
std: branchless bucket distance for hashmap
std: RawTable exposes a safe interface for HashMap
std: Split hashmap.rs into modules