Update to latest Rust

I haven't yet reached a point where I can run `make check` on
 Servo to test if this works, however these commits (fetched from upstream)
 seem to compile correctly. 


The next commit, which would bring
 us to upstream master doesn't compile and gives us the following error:

```
rust-http/src/codegen/main.rs:22:30: 22:39 error: failed to find an implementation of trait std::path::BytesContainer for &[&~str]
/home/muon/Desktop/Programming/Mozilla/servo/src/support/http/rust-http/src/codegen/main.rs:22             let output_dir = Path::new(args.get(2).as_slice());

```