Author: bcoudurier
   Date:   Sat Jul 3 03:11:04 2010 +0000

       Set graph swscale opts before parsing it, that way opts are available
       when auto-adding scalers.

It changed the swscale flags used by the auto-added scalers, and so
the output video.

Originally committed as revision 24065 to svn://svn.ffmpeg.org/ffmpeg/trunk