Adding a new AbilityUsesBlurBehind which can be set by decorations with
alpha channel to request that the background can be blurred. This improves
the situation for our completely opaque default Oxygen decoration.

This change is a behavior change in comparison to 4.5! Translucent decorations do
not get blurred by default any more.
CCMAIL: craig.p.drummond@googlemail.com

svn path=/trunk/KDE/kdebase/workspace/; revision=1195274