 Changes since telnetd-1.0:

  - plugged the most blatant security holes (NOTE: telnetd probably still
    cannot be considered "secure"):
     o added support for a simple (unix-style) password. The encrypted
       password is read from an environment variable or a hardcoded default.
     o limit the maximal number of simultaneous connections (this was
       implemented alread but a delay was added).
     o disconnect after some time if the peer doesn't send a password.
     o disconnect after a few authentication failures and send message
       to syslog.
     o syslog connection establishment/shutdown (#ifdef PARANOIA).

   - made 'PTY' a truly polling driver (at the expense of some CPU time -
     I use a pretty long polling interval, though [2s]). This makes e.g.
     termios VTIME work properly (unless VTIME < polling interval).
 
   - PTY now passes telnet CRLF through (use termios igncr to strip CR)
     but maps telnet CRNUL to CR.

   - "reentryfied" BSD '__des_crypt()'.

   - use more specific names for global symbols; 'localized' most
     private ones.
