matroskadec: silently skip CodecState element.

mkvmerge apparrently uses it for mpeg1/2 video, but it contains the same
information as CodecPrivate, so it can be ignored.

libavformat/matroska.h

@@ -176,6 +176,7 @@
 #define MATROSKA_ID_BLOCK      0xA1
 #define MATROSKA_ID_BLOCKDURATION 0x9B
 #define MATROSKA_ID_BLOCKREFERENCE 0xFB
+#define MATROSKA_ID_CODECSTATE 0xA4
 
 /* IDs in the attachments master */
 #define MATROSKA_ID_ATTACHEDFILE        0x61A7

libavformat/matroskadec.c

@@ -500,6 +500,7 @@ static EbmlSyntax matroska_blockgroup[] = {
     { MATROSKA_ID_SIMPLEBLOCK,    EBML_BIN,  0, offsetof(MatroskaBlock,bin) },
     { MATROSKA_ID_BLOCKDURATION,  EBML_UINT, 0, offsetof(MatroskaBlock,duration), {.u=AV_NOPTS_VALUE} },
     { MATROSKA_ID_BLOCKREFERENCE, EBML_UINT, 0, offsetof(MatroskaBlock,reference) },
+    { MATROSKA_ID_CODECSTATE,     EBML_NONE },
     { 1,                          EBML_UINT, 0, offsetof(MatroskaBlock,non_simple), {.u=1} },
     { 0 }
 };