Fix punctuation table

* src/pf/lang.lua: Fix punctuation table to not contain integers.
More lexer tests

* src/pf/lang.lua: More tests.
IPv4 lexing

* src/pf/lang.lua: Fix parsing of IPv4 addresses.
Add net lexing test

* src/pf/lang.lua: More tests.
Beginnings of parser

* src/pf/lang.lua: First pass at parser.