revert the previous change to how transparent pixels are handled
revert the previous change to how transparent pixels are handled

Turns out only transparent pixels on a BitmapData object that have never
been set work like this.
Who'd have thought? ;o

freedesktop-unofficial-mirror/swfdec__swfdec,mltframework/swfdec,mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec