a year before 1970 or a date beyond the time_t rollover, return -1 so callers
can detect it. Callers which expect the function not to fail just get a
different kind of rubbish from before.
Some of the stuff (e.g., rarpd, bootpd, dhcpd etc., libsa) still will
only support Ethernet. Tcpdump itself should be ok, but libpcap needs
lot of work.
For the detailed change history, look at the commit log entries for
the is-newarp branch.
christos