Enable WavPack decoding in ffmpeg (once they'll increment the version number)....

Enable WavPack decoding in ffmpeg (once they'll increment the version number). Some of the samples still decode weird but hey ... it's already great news :)

modules/codec/ffmpeg/ffmpeg.c

@@ -1111,6 +1111,11 @@ static struct
     { VLC_FOURCC('u','l','a','w'), CODEC_ID_PCM_MULAW,
       AUDIO_ES, "PCM ULAW" },
 
+#if LIBAVCODEC_BUILD >= ((51<<16)+(15<<8)+1)
+    { VLC_FOURCC('w','v','p','k'), CODEC_ID_WAVPACK,
+      AUDIO_ES, "WavPack" },
+#endif
+
     {0}
 };