Update to the last rust-nightly.

Version of rustc: 0.11.0-pre-nightly (faa7ba7 2014-05-31 01:06:40 -0700).

Main changes:
        * `cmp::Ord` -> `cmp::PartialOrd`
        * `cmp::Eq`  ->  `cmp::PartialEq`

Note that `na::PartialOrd` is not the same as `cmp::PartialOrd`
(which lacks a lot of partial ordering operators).