The clean_up() function is called by the driver on a regular basis in
all objects that have been inactive for the time specified for
clean_up() in the runtime configuration file. One flag is passed to
the function, specifying whether or not the object has been inheritted
by anything. If clean_up() returns 0, clean_up() will never be called
again on that object. If it returns 1, it will be called again when
the object remains inactive for the specified clean_up() delay.
One thing that might be commonly done by an object in this function is
destructing itself to conserve memory.