TTY_NETWORK (network), TTY_DIALUP (dialup), which determine a basic
connection type. TTY_DIALUP in particular will replace the old out of
date heuristic "tty[dD]*" in login.c (and better than the current
hard-coded method).
more manageable and convenient referencing by login.conf (login
class database) and (e.g.) login.access.
This is the first of a group of commits which implements the login
class capabilities database.
