Build fix for older ffmpeg versions.
Build fix for older ffmpeg versions.

svn path=/trunk/libavg/; revision=2903

scotty007/libavg,libavg/libavg,yyd01245/libavg,yyd01245/libavg,libavg/libavg,scotty007/libavg,th3infinity/libavg,scotty007/libavg,libavg/libavg,libavg/libavg,hoodie/libavg,hoodie/libavg,yyd01245/libavg,scotty007/libavg,th3infinity/libavg,hoodie/libavg,hoodie/libavg,yyd01245/libavg,th3infinity/libavg,th3infinity/libavg