AlbumGUI, Editor, BQM, ImportUI, LT:

simplify fullscreen action handling to use KToggleFullScreenAction
use toggled(bool) signal from action to prevent multiple fire to slotToggleFullScreen()
use KToggleFullScreenAction::setFullScreen() instead to change QWidget properties to swith on/off to full screen.
Fix crash under MACOSX
BUGS: 257773
FIXED-IN: 3.1.0