Fixed compile failure on older ffmpeg versions.
Fixed compile failure on older ffmpeg versions.

svn path=/trunk/libavg/; revision=9255

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