anchor.diff:  , vdpauSupport ? false, libvdpau ? null
   , cddaSupport ? !stdenv.isDarwin, cdparanoia ? null
   , dvdnavSupport ? !stdenv.isDarwin, libdvdnav ? null
  +, dvdreadSupport ? true, libdvdread ? null
   , bluraySupport ? true, libbluray ? null
   , amrSupport ? false, amrnb ? null, amrwb ? null
   , cacaSupport ? true, libcaca ? null
  
positive.code: assert vdpauSupport -> libvdpau != null;
  assert cddaSupport -> cdparanoia != null;
  assert dvdnavSupport -> libdvdnav != null;
  assert bluraySupport -> libbluray != null;
  assert amrSupport -> (amrnb != null && amrwb != null);
  assert cacaSupport -> libcaca != null;
  
negative.code:     ++ optional cacaSupport libcaca
      ++ optional xineramaSupport libXinerama
      ++ optional dvdnavSupport libdvdnav
      ++ optional dvdreadSupport libdvdread
      ++ optional bluraySupport libbluray
      ++ optional cddaSupport cdparanoia
      ++ optional jackaudioSupport libjack2
  