Include all non-Free firmware from Debian Wheezy

In a couple of cases this involves replacing Valve-supplied firmware, but
this isn't a big deal since they're rebuild-only on binary blob packages
(md5sums on actual firmwares should match).

$DEITY willing, this will fix installation for people on esoteric network
gear like Broadcom or Atheros.
Fix Issue https://github.com/directhex/steamos-installer/issues/14

This involves shipping a patched debootstrap package