Updated cx driver commit part 1: bring in the new kernel driver.

This is the vastly updated cx drvier from Roman Kurakin <rik@cronyx.ru>
who has been patiently waiting for this update for sometime.

The driver is mostly a rewrite from the version we have in the tree.
While some similarities remain, losing the little history that the old
driver has is not a big loss, and the re@ felt it was easier this way (less
error prone).

The userland parts of this update will be committed shortly.

The driver is not connected to the build yet. I want to make sure I
don't break any platform at any time, so I want to test that with
these files in the tree before I continue (on the off chance I'm
forgetting a file).

I changed the DEBUG macro to CX_DEBUG from the code that was submitted
(to not break when we go to building with opt_global.h after the
release), as well adding $FreeBSD$.

Submitted by: Roman Kurakin
Approved by: re@ <scottl>