Update Dockerfile to be based on 13.10 instead of 12.04, add linux-libc-dev dep, remove s3cmd backports nonsense

This is so that we can remove our s3cmd backports APT crap, and so we can have the new linux-libc-dev dependency we need for compiling the btrfs driver (#3718) without even more nasty APT hackery.

I have tested successfully compiling #3718 on top of this, and we're golden.