Invokable Classes as Event Handlers

Adding ability to use classes as event handlers

// ...
class HandleOnEvent
{
    // ...
    public function __invoke($args) {/*  ...event handler */}
    // ...
}

$SomeClassWIthEvents = new SomeClassWIthEvents;
$SomeClassWithEvents->onEvent[] = (new HandleOnEvent)('args normally passed to Closure')