issue #4129: EventDispatcher::_listeners -> _listenerMap.
issue #4129: Uses 'const reference' when getting touches by EventTouch::getTouches.
issue #4129: EventTouch::getTouches return const reference.
closed #4129: Event listeners in engine shouldn't be removed by method removeAllEventListeners().
issue #4129: Remove unused references in Xcode project.
issue #4129: Adds default argument(nullptr) for dispatchCustomEvent.
issue #4129: Adds test case for issue 4119.
Merge pull request #5492 from dumganhar/iss4129-remove-all-listener

closed #4129: Event listeners used in engine shouldn't be removed by method removeAllEventListeners().