(main_argp_parser): For login-auth-mode, we don't need a user
database. Instead use make_unix_user_self and
make_userauth_none_permit.
(install_session_handler): New command.
(lshd_login_service): Take the "session" channel open handler as
argument. We don't need a general list of connection hooks. Use
init_connection_service, not the reduntant init_login_service.
(make_lshd_login_service): Simplified a little.

Rev: src/lshd.c:1.160