this way it works on 64-bit archs too.
Patch by Jindřich Makovička ($lastname without last letter and háček, gmail)
Originally committed as revision 22093 to svn://svn.ffmpeg.org/ffmpeg/trunk
Reviewed and corrected by myself because there were no other volunteers in the
last weeks.
Originally committed as revision 21531 to svn://svn.ffmpeg.org/ffmpeg/trunk