serial port baud generator

[Jim Rees <rees_(_at_)_umich_(_dot_)_edu>]

Is there some bug in the speed setting code in com.c?  If I put std.9600 on
a com port in my /etc/ttys, that port is at 1200, not 9600.  If I write a
program that just opens /dev/tty00, sets it to 9600, and writes characters,
again they come out at 1200, not 9600.

I see comopen sets tp->t_ospeed to comdefaultrate, but doesn't actually set
the speed of the uart.  Only cominit does that, and I don't know where
that's called from.