This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
negation whenever we access memory between 640k and 1M.
Original code from NetBSD 1.0-BETA. The exact origins are unclear but
Theo de Raadt, Charles, and Michael V. may have contributed to it.
Submitted by: pst