Add CODEC_ID_GSM and CODEC_ID_GSM_MS to ffmpeg audio codec list. (mostly...

Add CODEC_ID_GSM and CODEC_ID_GSM_MS to ffmpeg audio codec list. (mostly useless but it doesn't hurt. needs ffmpeg to be linked with an specific lib)

modules/codec/ffmpeg/ffmpeg.c

@@ -944,7 +944,6 @@ static struct
       VIDEO_ES, "VMware Video" },
 #endif
 
-
     /*
      *  Image codecs
      */
@@ -1096,6 +1095,13 @@ static struct
       AUDIO_ES, "WavPack" },
 #endif
 
+#if LIBAVCODEC_VERSION_INT >= ((51<<16)+(34<<8)+0)
+    { VLC_FOURCC('g','s','m',' '), CODEC_ID_GSM,
+      AUDIO_ES, "GSM Audio" },
+    { VLC_FOURCC('g','s','m','s'), CODEC_ID_GSM_MS,
+      AUDIO_ES, "Microsoft GSM Audio" },
+#endif
+
     /* PCM */
     { VLC_FOURCC('s','8',' ',' '), CODEC_ID_PCM_S8,
       AUDIO_ES, "PCM S8" },