Feat: Error on undefined function
Fix: All ids are now prefix to prevent native var clashes.
This was already done on it2, but now also in it0 and it1.
Redid it2 to match.
Fix: generate-recipes would not complain on missing exp.
Fix: Adds documentation and test for not
Chore: __check helper function for ease of use in it0, it1.
Chore: some reordering to match more between iterations.
Feat: add now can add two full strings
Fix: it2 would have different working for emit eof
Fix: eq and lt would return bools on it0 and it1
Fix: Functions always return something (there is no such
thing as an empty type).
Fix: Return value from main is now always ignored.
Fix: Output from check is same on all iterations
