- added test for indirect left recursion: ilr works with DHParser but stresses python's recursion depth limit

containing parsers), because caching does not keep track of the state
of variables.

- syntaxtree.py: transformation_factory decorator for processing table functions; further type annotations

- parser.py: bug: pos values not initialized in nodes in history record, in case root parser did not match

- example MLW extended by adding rudimentary testcases