Removing disconnected tty drivers

[John Baldwin]

The following drivers have never been converted to use the new tty layer 
introduced in 8.0 and have been disconnected since then.  Several of them are 
for older multiport serial cards, and in the case of sio(4), current kernels 
use uart(4) instead.  Barring major objections, I plan to remove them from the 
tree later this week.  If someone wishes to update them, they can always be 
pulled back from svn history.

dev/cx/if_cx.c:         d->tty = ttyalloc ();
dev/cy/cy.c:                    tp = com->tp = ttyalloc();
dev/digi/digi.c:                tp = port->tp = ttyalloc();
dev/rc/rc.c:            tp = rc->rc_tp = ttyalloc();
dev/sio/sio.c:  tp = com->tp = ttyalloc();
pc98/cbus/sio.c:        tp = com->tp = ttyalloc();

-- 
John Baldwin