Adds divx/xvid encoders. divx encoder is based on divx4linux (commercial, closed...

Adds divx/xvid encoders. divx encoder is based on divx4linux (commercial, closed-source)

Original commit message from CVS:
Adds divx/xvid encoders.
* divx encoder is based on divx4linux (commercial, closed-source)
* xvid encoder is based on xvidcore (http://www.xvid.org/, GPL - Christian? ;) )

Both use a GstCaps that doesn't conform with what we currently use, I might fix that later on or so. For now, it doesn't matter, it's just a test. We're also missing corresponding decoders (ffmpeg can decoded this too, but that's not the point), these might come later too.