New package lex.el.
* packages/lex/lex-parse-re.el: New file, extracted from lex.el.
* packages/lex/lex.el: Use it instead of the self-load hack.
(lex--nfa, lex-compile): Use case-table-get-table.
* lex.el: Compatibility fix
Only keep the strictly necessary *-pkg.el files
* packages/lex/lex.el: Use lexical-binding.