GUI Control - Event Handlers

9 scripting commands. Also as Markdown for agents.

ctrlAddEventHandlerAdd an event handler to the given control.
ctrlRemoveAllEventHandlersRemove all event handlers from the given control.
ctrlRemoveEventHandlerRemove a given event handler from the given control.
ctrlSetEventHandlerSets given event handler of given control: any previously added event handler is removed.
displayAddEventHandlerAdds an event handler to the given display. See User Interface Event Handlers for the full list of event names.
displayRemoveAllEventHandlersRemove all event handlers from the given display.
displayRemoveEventHandlerRemove a given event handler from the given display.
displaySetEventHandlerSets given event handler of given display. The return code of the provided function should indicate whether this event was handled correctly.
inGameUISetEventHandlerSets given event handler of in-game UI. If EH function returns true, performed action is overridden.