Tracking the dependency DAG of mplayer2 lead to a big series of patches.
These are the fairly simple first 21 out of a total 25.  I will push
them in let's say two days if nobody has comments.

5 of the patches do something else than adding a package:

- openal has been moved from games to audio,

- freeglut now propagates input glu,

- cdio had a misleading description claiming it includes pycdio and
  libcdio-paranoia, when it doesn't; it's now fixed,

- ffmpeg got three more optional inputs that were already packaged,

- ffmpeg now builds with libavresample support.

Moreover, a handful of the package-adding patches also add the added
package as an additional optional input to ffmpeg.

The patches: