acorn32 console changes

[Chris Gilbert <chris%dokein.co.uk@localhost>]

FYI,

over the past few weeks I've been updating the acorn32 console code in 
-current to hopefully improve it's usability.  Highlights include:
* virtual console support added.  To enable make sure wscons=YES is in 
your /etc/rc.conf, then use ctrl-alt-fx to switch console
* colour console.  I've set the flag to indicate we can do colour on the 
console
* console scrollback. shift+page-up and shift+page-down should scroll 
the console up and down
* kernel messages are in green, so they stand out
* the default font is the default NetBSD 8-pixel wide font, rather than 
the sony one we previously used.
* Console beep - fixed a 3 year old bug that stopped beep working on the 
console.
* only take vsync interrupts when we've something to do (less overhead 
on system)

It should be noted that most of these items can be tuned using kernel 
parameters and wscons utilities.

One caveat is that I've not tested these changes with an X server yet, 
so it's possible I might have broken something, but I'm hoping I haven't.

Changes were tested on an A7000+ and SA Risc-PC with 2MB VRAM at 800x600 
in 8bpp colour.

Known issues:
* 4bpp colour isn't working for some reason, need to investigate
* scrollback only works after switching virtual console.

Feedback (positive or negative :) would be good.

Thanks,
Chris