Hi all,

I've committed some prelimiary changes for the pmax console code into
-current. These address most of the problems in pr #4438.

Michael Hitch and I have tested these on MAXINE, 3MIN, and 3100, with
raster consoles, and with serial consoles on the 3MIN and MAXINE.  As
far as this change is concerned, the 3MAXPLUS (5000/240, 5000/260)
should be the same as the 3MIN (5000/1xx), and the 5000/200 should be
the same as the 3100.  I would test it on more machines, but that's
all I have access to right now.

For now, this only affects people running -current.  But since the
console code causes persistent overrun -- even with the
recently-announced scc.c patches -- I'd like to get this fixed and
pulled up into any future 1.3.2 release.

As usual, if anyone sees problems, please send a PR.  Given that any
problems tend to stop machines booting, an emial here might not be
amiss, either.