Current tree has all allocated ports on portlist.  However,
most of the portlist users assume that we only have announced ports
there and break badly if they happen to see the list after port driver
has created a port (parport_register_port()) but before it finishes
the setup (and calls parport_announce_port()).
	The only place that wants to see all allocated port is
parport_register_port() itself and only to pick the first unused
port number.
	We add a new list (all_ports) and put ports there when allocated;
that list is kept ordered by port->number.  Ports are placed on portlist
only by parport_announce_port().
	Gobs of shite in parport_register_port() removed, pile of races
closed...