Another step towards user-land drivers

[Samuel Thibault]

Hello,

So thanks to Damien's polishing work, we got an acceptable
userland-driver interface which I could commit mainstream. I have just
uploaded in Debian a GNU Mach version 1.8+git20200710-1 that includes
it. We now have to fix netdde and rump into using that proper interface.

That's yet another step towards user-land drivers: we already have
network drivers, Damien is working on disk drivers. Once we have that
working, we will be able to get rid of the old Linux piece included in
the gnumach source, that is currently only used for the disk support.

Samuel