Fixes to:

 1) retain the buffered/unbuffered line specific details across save/restore
 2) retain modem control outgoing bits (CTS and DTR) accross line resets which may occur due to carrier/connection loss.
 3) change the behavior which sends  the prior contents of the transmit buffer on a line reconnect to only happen for buffered telnet lines.
 4) avoid crash in SHOW MULTIPLEXER output when only specific lines have been attached instead of