yasm 1.2.0

[chriswiggins]

Not that it's needed for ffmpeg now, but if we are ever going to include x264 in the puppet build system, we'll need to use yasm 1.2.0 as the yasm 1.1 in the Ubuntu 12.04 repository is not compatible:

root@host:/usr/local/src/x264# ./configure --enable-static
Found yasm 1.1.0.2352
Minimum version is yasm-1.2.0

This can be fixed by installing yasm 1.2.0. Do you want a pull request for this?