Turns out the cores on Apple's M1 SoC only support 8-bit ASIDs.

Turns out the cores on Apple's M1 SoC only support 8-bit ASIDs.
Thank you Apple (not)!

Add an initial attempt to support such systems.  This isn't good enough
since the kernel will hang once you create more than 127 processes.
But it makes things work reasonably well until you reach that limit
which is good enough to build things on the machine itself.

ok patrick@