easily, and so that the original (insque/remque) logic can be effectively
mimiced. (This fixes a bug in the previous set of list changes.)
also (since terminator is no longer null) reinstate uninitted list checks,
but mark them XXX.
* Convert several data structures to use queue.h.
* Split in_pcbnotify() into two parts; one for notifying a specific PCB, and
one for notifying all PCBs for a particular foreign address.