Cancel the event having the specified handle. Return 0 on successful cancellation, and a non-zero value if the handle is invalid or if the event has already been dispatched or canceled. Note that due to the implicit conversion from Handle types, these methods also match the following: ` int cancelEvent(const EventHandle& handle); int cancelEvent(const RecurringEventHandle& handle); ` Compared to the version taking a pointer to Handle, the managed reference to the event is not released until the Handle goes out of scope.