quartz: update the keymap only if the input method changed
quartz: update the keymap only if the input method changed

and not on each keystroke, which for some IMs apparently caused a full
update on each keystroke, not just a check for changes. Patch from
Takuro Ashie, bug #698183.

Distrotech/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk