events - a simple event dispatcher

• Include events.h
• Create your event classes like class my_event : event { ... }
• Instantiate the dispatcher.
• Define a listener like result my_event_handler_function (my_event * e) { ... }
• Register (or unregister) your listeners like my_dispatcher.register_listener (&my_event_handler_function);
• Send events to dispatcher and watch them flow like my_dispatcher (new my_event{});
• test.cpp is here to provide useful examples