kernel threads as threads.

I have made a first set of changes to allow threads to be 'forked' 
within the kernel.

I have run on the resulting kernel for some of today with no problems 
other than
some statistics oddness in top which I plan on looking at next week.

The current patch doen't remove the ability to make kernel processes, 
however it does
add the ability to make threads under process 0 and alters nearly all 
the users of
kernel threads to actually do this.. The exception is the aio threads, 
as they seem to require
separate address spaces to work with and that requires separate proc 
structures.

I was thinking that they could act as extra threads on the calling 
processes but that
is more of a rewrite than I plan right now.

Anyhow the diffs so far are at:

http://www.freebsd.org/~julian/kthread.diff.

more later.

julian