is different than the "machinename" internal variable, read
machinearch's files.${machinearch} and add it to the list of files
for the machine. Also, regardless of whether or not they're different,
create a ${machinearch} sylink (or directory) pointing to the machinearch
include files (or containing them).
2. "irq ?" sets it to (u_short)-1
3. "irq #" sets it to (1<<#)
4. not specifying an interrupt sets it to 0.
Until someone else comes up with a better scheme, that's the way it is.
If you have a driver that turns the interrupt off, set it to ZERO.
If, after calling XXprobe(), id_irq is still (u_short)-1, that is the same
as if XXprobe() failed.
thorpej