Prepare gif decoder for use in conjunction with gif demuxer.

Add capability of reading multiple frames instead of only first.
Implement support for different gif frame 'disposal methods'.
Add option that allows to change background color resulting from
conversion of gif with transparency to any other format which
not support it.
Also bump lavc minor version.
Signed-off-by: Vitaliy E Sugrobov <vsugrob@hotmail.com>

libavcodec/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 54
-#define LIBAVCODEC_VERSION_MINOR 77
-#define LIBAVCODEC_VERSION_MICRO 101
+#define LIBAVCODEC_VERSION_MINOR 78
+#define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \