[kcms/keyboard] Restore keyboard layout OSD on X11
OSD for Alternative shortcut has been removed in 9021b3cb, because that approach didn't work well with new layout applet.
Here we restore it with original behavior - the OSD is shown when the shortcut is invoked, but not when used via
the applet.
NOTE: fixes "Alternative shortcut" only! Main shortcuts (and possibly 3rd level shortcuts) still yet to be implemented.
Edited by Andrey Butirsky