(OPEN 'TTY:) on Twenex

[JAR at MIT-MC (Jonathan A. Rees)]

Due to a Twenex bug, this actually gets the terminal itself rather than
the terminal or PTY which is the process's primary input.  It would
be nice if Maclisp fixed this for the user - this can be done using
the SCTTY JSYS; it returns either 777777 which means you can open
TTY: or it returns 400xxx which means you should open TTYxxx:.  This
is what I'm doing currently although there might be a cleaner means,
like using JFN 101 or whatever.  Also DEC might get around to fixing it.
In the meantime any help is appreciated... thanx.