Do not auto-detect Sorenson Spark in f4v.

Assuming codec_tag H263 for FLV only leads to trouble.

libavformat/isom.c

@@ -204,7 +204,7 @@ const AVCodecTag codec_movvideo_tags[] = {
 
     { CODEC_ID_DIRAC, MKTAG('d', 'r', 'a', 'c') },
     { CODEC_ID_DNXHD, MKTAG('A', 'V', 'd', 'n') }, /* AVID DNxHD */
-    { CODEC_ID_FLV1,  MKTAG('H', '2', '6', '3') }, /* Flash Media Server */
+//  { CODEC_ID_FLV1,  MKTAG('H', '2', '6', '3') }, /* Flash Media Server */
     { CODEC_ID_MSMPEG4V3, MKTAG('3', 'I', 'V', 'D') }, /* 3ivx DivX Doctor */
     { CODEC_ID_RAWVIDEO, MKTAG('A', 'V', '1', 'x') }, /* AVID 1:1x */
     { CODEC_ID_RAWVIDEO, MKTAG('A', 'V', 'u', 'p') },