This is long overdue. The device events are InternalEvents now (and only one
at a time), diminishing the need for an EventList for the master event.
Furthermore, don't make masterEvent a static since this will interfere if
mieqProcessDeviceEvent is called from somewhere else (e.g. XKB actions).
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>