Add parsing for "ether"

* src/pf/lang.lua: Fix lexing for IPv6 addrs, add ehost lexing, and add
  ether parser.
More parsers

* src/pf/lang.lua: Add parsers for gateway, net, port, portrange, less,
  greater, ip, ip6, proto, tcp, udp, and icmp.
More parsers

* src/pf/lang.lua: Add parsers for protochain, arp, rarp, atalk, aarp,
  and decnet.
More parsers (blah!)

* src/pf/lang.lua: Add a slew of new parsers.
Finish primitives parser

* src/pf/lang.lua: Finish adding parser types