FEAT: automatic breaking out of a loop if input has not advanced (prevents some common infinite loops errors).
FIX: PARSE's NOT wrong branching in the FSM.
FIX: PARSE's REJECT and BREAK bugs.
TESTS: added some tests for FAIL, NOT, QUOTE, REJECT, NONE
FIX: issue #481 (WITH can't find symbols in cascaded CONTEXTs)