ShadowedBackground background hint

[Marco Martin]

Hi,
discussing with Kevin about the translucent background hint in Plasma::Applet, 
it has emerged that one of the hints that are now present, ShadowedBackground
is totally fake, because the code for shadow, is really broken and ifdeffed 
out right now.
since i don't see very realistic to fix shadows for 4.1, probably it would be 
better removing it, at least commenting it out for now, to not create 
a "false" api,
comments? opinions?

Cheers,
Marco Martin