gdkevents-win32.c: Fix GDK_SETTING event notification on IME change

We need to call g_strdup() on the name that we pass in for notifying the
GDK_SETTING event so that when we do gdk_event_free() later we will not
get a crash (stack corruption) that results from attempting to g_free()
something that is not dynamically allocated.
2 jobs for gtk-3-24.ime-event.fixes in 10 minutes and 6 seconds (queued for 2 seconds)