closes [misc/543] and [bin/1295]
- syslog() failures of iruserok(), which should help debugging why
a .rhosts authentication failed.
- log a successful iruserok() if -L given. idea from rshd(8).
- allow root .rhosts to authenticate, the same way that rshd(8) does.
the prior behaviour meant that 'rsh foo csh -i' could get a shell
without a password, but 'rlogin foo' couldn't; very inconsistant.
closes [bin/1078] and [bin/1239]
