Implement missing lowering operators

Currently only a small subset of lowering operators are implemented.  This set should be made complete.  Happily it's not too difficult -- you just compile an expression with libpcap, cross-compile to Lua using the pflua bpf compiler, look at the generated code, then make the pflang compiler do something similar.
can't you start an ipv6 address with 0 or 1 hex characters?  i think so, e.g ::1 for loopback