Add missing D_TTY flags to various drivers.
Complete asserts that dev_t's passed to ttyread(), ttywrite(),
ttypoll() and ttykqwrite() have (d_flags & D_TTY) and a struct tty
pointer.
Make ttyread(), ttywrite(), ttypoll() and ttykqwrite() the default
cdevsw methods for D_TTY drivers and remove the explicit initializations
in various drivers cdevsw structures.
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>
