xmon cuda support for 2.2.17

hi,

here is an quick hack that gets cuda support into xmon for 2.2.17 (Ben's)
although it should work OK on linux-pmac-stable as well. It should really
be done like 2.4.0 (but I needed it in a hurry).

It also adds a tee to push stuff to the serial port as well as the screen - so that you can debug using the screen but, if it all goes horribly wrong, still collect output on a terminal emulator etc.

you need the patched via-cuda.c as well [previous mail] (although only a small part of that is necessary for xmon support).

ciao,
Iain.