Bump minor after read/write_line() to av_read/write_image_line()

rename, done in r24101.

Originally committed as revision 24128 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/avutil.h

@@ -40,7 +40,7 @@
 #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
 
 #define LIBAVUTIL_VERSION_MAJOR 50
-#define LIBAVUTIL_VERSION_MINOR 20
+#define LIBAVUTIL_VERSION_MINOR 21
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \