anchor.diff:      ++ optional pulseSupport libpulseaudio
       ++ optional resamplerSupport libsamplerate
       ++ optional overloadSupport zlib
  +    ++ optional midiSupport wildmidi
       ++ optional wavpackSupport wavpack
       ++ optional remoteSupport curl
       ;
  
positive.code: assert pulseSupport -> libpulseaudio != null;
  assert resamplerSupport -> libsamplerate != null;
  assert overloadSupport -> zlib != null;
  assert wavpackSupport -> wavpack != null;
  assert remoteSupport -> curl != null;
  
  
negative.code: , wavSupport ? true, libsndfile ? null
  , cdaSupport ? true, libcdio ? null, libcddb ? null
  , aacSupport ? true, faad2 ? null
  , midiSupport ? false, wildmidi ? null
  , wavpackSupport ? false, wavpack ? null
  , ffmpegSupport ? false, ffmpeg ? null
  # misc plugins
  