Revert "contrib: vpx: update to 1.2.0"

This reverts commit 7e2edc0d901a4ffe1fc429a81cccdb69dc186372.

http://webm.googlecode.com/files/libvpx-v1.1.0.tar.bz2
 is a release tarball
http://webm.googlecode.com/files/libvpx-v1.2.0.tar.bz2
 is a daily updated git snapshot

libvpx has no release tarballs (or releases) anymore apparently.