Handle missing query
Mark unused operator<< with __attribute__ ((used))
Fix -[child offset]
Throw an exception for invalid tokens in lexer
Drop unnecessary %option nodefault from lexer
Introduce -O0
Fix N/-X

- This caused assertion failures at runtime.  The problem was that N/
  didn't overtake the popped slots, and later protect took new slots
  from N/'s pool.  After exhausting the formerly-N/'s pool, more
  uninitialized slots were generated.

- The solution is to return the list of dropped slots and leave N/ be
  in control of that.