pseudo codec tag for adpcm_swf

Originally committed as revision 3981 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/wav.c

@@ -39,6 +39,7 @@ const CodecTag codec_wav_tags[] = {
     { CODEC_ID_SONIC, 0x2048 },
     { CODEC_ID_SONIC_LS, 0x2048 },
     { CODEC_ID_ADPCM_CT, 0x200 },
+    { CODEC_ID_ADPCM_SWF, ('S'<<8)+'F' },
     { 0, 0 },
 };