Remove xine plugins, not very well supported and gstreamer-ffmpeg does a
better job.
Override COMMENT and PORTREVISION in slave ports.
For the slave ports in multimedia add also CATAGORIES.
Chase libmusepack -> libmpcdec rename.
Changelog: http://gstreamer.freedesktop.org/releases/gst-plugins/0.8.9.html
Approved by: maintainer (implicit)