Canopus HQX decoder

Based on work by Kostya Shishkov <kostya.shishkov@gmail.com>.

libavformat/riff.c

@@ -351,6 +351,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_PRORES,       MKTAG('A', 'P', 'C', 'N') },
     { AV_CODEC_ID_PRORES,       MKTAG('A', 'P', 'C', 'H') },
     { AV_CODEC_ID_QTRLE,        MKTAG('r', 'l', 'e', ' ') },
+    { AV_CODEC_ID_HQX,          MKTAG('C', 'H', 'Q', 'X') },
     { AV_CODEC_ID_NONE,         0 }
 };