Fixed build for older ffmpeg.
Fixed build for older ffmpeg.

svn path=/trunk/libavg/; revision=8768

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