Add APIchanges entry after the addition of av_fill_image_max_pixstep()

of r24827.

Originally committed as revision 24828 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2009-03-08
 
 API changes, most recent first:
 
+2010-08-18 - r24827 - lavcore 0.5.0 - av_fill_image_max_pixstep()
+  Add av_fill_image_max_pixstep() in imgutils.h.
+
 2010-08-17 - r24814 - lavu 50.24.0 - AV_NE()
   Add the AV_NE macro.