Update to build with latest rustc.

Includes fixes for `format!` changes, and removal of one last `~[]` in pcredemo.

Builds with:

    $ rustc --version
    rustc 0.11.0-pre (4b672a6 2014-06-16 17:01:56 +0000)
    host: x86_64-unknown-linux-gnu
Merge pull request #18 from am0d/rustc

Update to build with latest rustc.

    $ rustc --version
    rustc 0.11.0-pre (4b672a6 2014-06-16 17:01:56 +0000)
    host: x86_64-unknown-linux-gnu
Add `#![feature(unsafe_destructor)]`
Fix bare raw pointers (switch to `*const T`)