returns the state set by the user - these two may differ e.g. while hover-unshaded.
Therefore titlebar buttons should use isSetShade(), otherwise they become
a bit useless with hover-unshading.
Also fix updating the button state - the styles duplicate way too much code,
and if one of them has a bug, most of them definitely have it as well. Some
of the code should probably move to the decoration lib :-/ .
svn path=/trunk/kdebase/kwin/; revision=366147
9a5a1c5d95