Do not set codec_tag property for matroska muxers.

Fixes ticket #8.

libavformat/matroskaenc.c

@@ -1235,7 +1235,6 @@ AVOutputFormat ff_matroska_muxer = {
     .write_packet      = mkv_write_packet,
     .write_trailer     = mkv_write_trailer,
     .flags             = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS,
-    .codec_tag         = (const AVCodecTag* const []){ff_codec_bmp_tags, ff_codec_wav_tags, 0},
     .subtitle_codec    = CODEC_ID_SSA,
     .query_codec       = mkv_query_codec,
 };
@@ -1274,6 +1273,5 @@ AVOutputFormat ff_matroska_audio_muxer = {
     .write_packet      = mkv_write_packet,
     .write_trailer     = mkv_write_trailer,
     .flags = AVFMT_GLOBALHEADER,
-    .codec_tag = (const AVCodecTag* const []){ff_codec_wav_tags, 0},
 };
 #endif