anchor.diff:        (mkFlag shoutSupport "shout")
         (mkFlag sqliteSupport "sqlite")
         (mkFlag curlSupport "curl")
  -      (mkFlag soupSupport "soup")
         (mkFlag audiofileSupport "audiofile")
         (mkFlag bzip2Support "bzip2")
  -      (mkFlag (!stdenv.isDarwin && ffadoSupport) "ffado")
         (mkFlag ffmpegSupport "ffmpeg")
         (mkFlag fluidsynthSupport "fluidsynth")
         (mkFlag zipSupport "zzip")
  
positive.code:     ++ opt shoutSupport libshout
      ++ opt sqliteSupport sqlite
      ++ opt curlSupport curl
      ++ opt soupSupport libsoup
      ++ opt bzip2Support bzip2
      ++ opt audiofileSupport audiofile
      ++ opt (!stdenv.isDarwin && ffadoSupport) ffado
      ++ opt ffmpegSupport ffmpeg
      ++ opt fluidsynthSupport fluidsynth
      ++ opt samplerateSupport libsamplerate
  
negative.code: , shoutSupport ? true, libshout
  , sqliteSupport ? true, sqlite
  , curlSupport ? true, curl
  , audiofileSupport ? true, audiofile
  , bzip2Support ? true, bzip2
  , ffmpegSupport ? true, ffmpeg
  , fluidsynthSupport ? true, fluidsynth
  , zipSupport ? true, zziplib
  