bitmap header lookup: add code comment

Signed-off-by: rogerdpack <rogerpack2005@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/riff.c

@@ -28,7 +28,10 @@
 #include "libavutil/avassert.h"
 
 /* Note: when encoding, the first matching tag is used, so order is
-   important if multiple tags possible for a given codec. */
+   important if multiple tags possible for a given codec.
+   Note also that this list is used for more than just riff, other
+   files use it as well.
+*/
 const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_H264,         MKTAG('H', '2', '6', '4') },
     { AV_CODEC_ID_H264,         MKTAG('h', '2', '6', '4') },