TODO

- Lexer001Test in Python suite shows Lexer as Iterator. Implement that in PHP
- Refactor out expected tokens (type + text) iteration in the test into an assertion
- Refactor `State` into BaseRecognition Class (like in Python)
- Refactor `RuleReturnScope` into arrays?
- There are some $MEMO_* static variables, can we optimize them away somehow?

- Implement trivial examples to test Lexer and Parser, then switch to AST 
generation, and then to full sync with ANTLRv3

- Add implementation of StringTemplate class in PHP 
  (StringTemplateGroup for cminus example)

- Add codegeneration files AST.stg ASTParser.stg ASTTreeParser.stg ST.stg AST.stg ASTTreeParser.stg

- examples: *See TODO in each subfolder.