Add maxrate and bufsize specifications for iPod presets. I omitted these

originally as I thought x264 set these automatically when specifying a level.

Originally committed as revision 16629 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffpresets/libx264-ipod320.ffpreset

@@ -2,3 +2,5 @@ coder=0
 bf=0
 flags2=-wpred-dct8x8
 level=13
+maxrate=768000
+bufsize=3000000

ffpresets/libx264-ipod640.ffpreset

@@ -3,3 +3,5 @@ bf=0
 refs=1
 flags2=-wpred-dct8x8
 level=30
+maxrate=10000000
+bufsize=10000000