* build fribidi for the debian package
* add dependencies to debian package taking cues from the official debian version
  enable everything except:
  + libsdl2 (not available in wheezy or precise)
  + libmpeg123 (build error on precise due to old version)
  + caca, radio interface, openal output, portaudio output,
    rsound/libroar/sndio input/output, sdl1, joystick, videoio.h/libpt
* additional ffmpeg features (and dependencies) are still to be handled
  manually by the builder using the ffmpeg_options file as described
  in README.rst
* adjust debian/changelog so building works on both debian and ubuntu
  (tested on saucy,precise,wheezy,sid amd64)
* tweak debian parts of README.rst