Revert peter's commit to remove cdevsw_add() - it was a bit premature since things fail to function properly without it (pty allocation becomes somewhat haphazard).
Revert peter's commit to remove cdevsw_add() - it was a bit premature
since things fail to function properly without it (pty allocation becomes
somewhat haphazard).

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase