branches: 1.1.2; 1.1.6; 1.1.14; 1.1.16;
Add initial support for userspace block/char device drivers. This
is a very rough cut supporting only open/close/read/write for char
devices for the time being. It also takes some extra liberties in
error value processing wrt. to the request-response protocol, but
that will be fixed later. On the bright side, I haven't managed
to crash my test kernel in several hours with this anymore, so it
can be considered extra-stable ... All in all this is remarkably
similar to puffs from multiple angles (well, actually, big surprise
there) and these two will share more and more code in the future.

The hardest part, coming up with the name, was done by agc. I'm
not exactly sure what "pud" is supposed to stand for, but if my
British is anything close to par, I understand that "pud" over
there can stand for just about anything, so it's a safe bet.