Make ff_mkv_codec_tags array const, it is never written.

Originally committed as revision 11137 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/matroska.c

@@ -21,7 +21,7 @@
 
 #include "matroska.h"
 
-CodecTags ff_mkv_codec_tags[]={
+const CodecTags ff_mkv_codec_tags[]={
 //    {"V_MS/VFW/FOURCC"  , CODEC_ID_NONE},
     {"V_UNCOMPRESSED"   , CODEC_ID_RAWVIDEO},
     {"V_MPEG4/ISO/ASP"  , CODEC_ID_MPEG4},

libavformat/matroska.h

@@ -191,6 +191,6 @@ typedef struct CodecTags{
 /* max. depth in the EBML tree structure */
 #define EBML_MAX_DEPTH 16
 
-extern CodecTags ff_mkv_codec_tags[];
+extern const CodecTags ff_mkv_codec_tags[];
 
 #endif /* FFMPEG_MATROSKA_H */