Source headers point to wrong copyright file

Looks like this.

```
// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
```

'http://rust-lang.org/COPYRIGHT' does not and has not ever existed.

Best just to fix this with a redirect to the proper file on `www.` if we can.
