ip.h from plan 9

We need an ip stack and I understand the one we have is not that solid.
The one from Plan 9 is pretty good, and life will be easier if we have it.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Add the NIX ip stack

Known to work and probably better than what we've got.
You can build as it is commented out. One file already compiles.
See the Kbuilds.

We need to work out how to do a rendezvous, but other than that
there are no surprises here.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>