Add APIchanges for av_fill_image_max_pixstep() rename of r24851.

Originally committed as revision 24852 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2009-03-08
 
 API changes, most recent first:
 
+2010-08-20 - r24851 - lavcore 0.6.0 - av_fill_image_max_pixsteps()
+  Rename av_fill_image_max_pixstep() to av_fill_image_max_pixsteps().
+
 2010-08-18 - r24827 - lavcore 0.5.0 - av_fill_image_max_pixstep()
   Add av_fill_image_max_pixstep() in imgutils.h.