NETHER, NFDDI, NARC are not used anywhere. Remove #include "ether.h",
which had no effect.
Removes clash with "options NATM" for native-ATM network protocol stack.
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.
