initial seek support

Originally committed as revision 2502 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avi.h

@@ -13,6 +13,9 @@
 #define AVI_MAX_RIFF_SIZE       0x40000000LL
 #define AVI_MASTER_INDEX_SIZE   256
 
+/* index flags */
+#define AVIIF_INDEX             0x10
+
 offset_t start_tag(ByteIOContext *pb, const char *tag);
 void end_tag(ByteIOContext *pb, offset_t start);