/**
 * Append an orthogonal area of cleared tiles in _cleared_object_areas, then return with the list.
 * @param cleared_tile The tile being cleared, which then causes the whole object to be cleared.
 * @param coa_tile The top most tile of the area to be appended as cleared.
 * @param coa_w The width (x) of the area to be appended as cleared.
 * @param coa_h The height (y) of the area to be appended as cleared.
 * @return coa The _cleared_object_areas with the appended cleared area.
 */
ClearedObjectArea *MakeClearedObjectArea(TileIndex cleared_tile, TileIndex coa_tile, uint coa_w, uint coa_h)
{
	ClearedObjectArea *coa = FindClearedObject(cleared_tile);
	if (coa == NULL) {
		coa = _cleared_object_areas.Append();
		coa->first_tile = cleared_tile;
		coa->area = TileArea(coa_tile, coa_w, coa_h);
	}
	return coa;
}