issue #2087: Init Event::_userData.
issue #2087: Bug fix in EventDispatcher: _isRegister fix.
issue #2087: Adding new EventDispatcher Test.
   1) RemoveListenerWhenDispatching
   2) CustomEventTest
   3) LabelKeyboardEventTest
   4) SpriteAccelerationEventTest
issue #2087: Enabling acc when testing it.
issue #2087: Renaming EventDispatcherTest name to EventDispatcherTest(NEW)
Merge pull request #3696 from dumganhar/iss2087-new-event-dispatcher

issue #2087: Adding  new event dispatcher test and bug fixes.