Fix for NME target

[hoseyjoe]

cant compile currently need to add return types. if you need a project:
HaxeUITest.zip

haxe/ui/backend/ScreenImpl.hx:67: lines 67-73 : Field addComponent overrides parent class with different or incomplete type

Fix is to add
return component;

...
public override function addComponent(component:Component) {
		component.scaleX = Toolkit.scaleX;
		component.scaleY = Toolkit.scaleY;
		_topLevelComponents.push(component);
		container.addChild(component);
		onContainerResize(null);
		return component;
	}

	public override function removeComponent(component:Component) {
		_topLevelComponents.remove(component);
		container.removeChild(component);
		return component;
	}
...

[hoseyjoe]

This is working now