Adapted FilterUnmultiplyAlpha so transparent pixels work with bilinear filtering (#471).
Adapted FilterUnmultiplyAlpha so transparent pixels work with bilinear filtering (#471).

svn path=/trunk/libavg/; revision=9479

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