Lfun:	forbid_item_leave - forbid an item to leave a container

Synopsis:
	int forbid_item_leave(object item)

Description:
	The forbid_item_leave function is called in a container before
	an item tries to leave it, for example if a player wants to get it
	from.

Return value:
	Return 1, if the item mustn't leave the container, 0 if it may.

Examples:
	An container that keeps its gem:

	forbid_item_leave(item) {
		if (item->id("gem")) return 1;
	}

See also: object/notify_item_enter, object/notify_item_leave, object/forbid_item_enter, object/notify_enter_container, object/notify_leave_container, object/forbid_enter_container, object/forbid_leave_container, object/drop, object/get, efun/move_object, efun/transfer