knetd.conf needs to have an entry for the service demanded in
rlogin's GetKerberosData request.
also, Kerberos needs to know how to provide tickets for this service.

likewise, inetd needs to know about 4.3bsd rlogind service. see rlogin's
getservbyname calls.

to test rlogin:
* try rlogin both with and without Kerberos tickets.
* check that window-size changes are correctly-propagated: "man csh" should
  work nicely when the screen-size changes midway through.
* check that DISPLAY propagates on Kerberos-authenticated rlogins.
  use printenv, since DISPLAY should show first in the list.
* check that rlogin can connect vi inetd service, by calling up
  a machine which has only ucb rlogin service.
