Upgrade Rust

Brings us to [`9f8d2205f0518389993a9b5de6646ba8b14e5a12`](https://github.com/rust-lang/rust/tree/9f8d2205f0518389993a9b5de6646ba8b14e5a12) (June 17)


```
$ rustc --version
rustc 0.11.0-pre (d190aa1 2014-06-17 19:28:07 +0530)
host: x86_64-unknown-linux-gnu
```
(The commit hash and date are non-standard and from the mozilla-servo/rust repository)

This version of Rust includes some llvm-handling changes that let us use llvm-3.4 instead of 3.5 if necessary for the snapshots.

Needs OSX/Android fixes (and some of the submodule changes are still in PRs for the repos I don't have access to)

Also, someone needs to hit the retry button on [the osx snapshot build](https://travis-ci.org/mozilla-servo/rust/jobs/27775942), it ran out of time.