Unprivileged Subhurds

[Justus Winter]

Hello,

I'm trying to get unprivileged Subhurds to work.  The first part of
the puzzle is in fact a tiny kernel patch to provide a robust parental
relationship of tasks to userspace.  Currently, /hurd/proc relies on
posixesque processes to call proc_child to form a process hierarchy.

I've written about these notifications back in my gsoc days:

http://lists.gnu.org/archive/html/bug-hurd/2013-09/msg00170.html

I've got a patched up proc server and a boot program that do boot a
non-privileged Subhurd.  It actually bootstraps the core Hurd servers,
and starts `runsystem', but then the Subhurds proc server crashes.

Overall it's looking good, time to get the discussion going.

Cheers,
Justus