Fixed Image::disconnect PBO handling.
Fixed Image::disconnect PBO handling.

svn path=/trunk/libavg/; revision=1701

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