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