To fix XFA language_contains, I must first break it
Mark off failing test cases
KeyedSemElemSet: omit zero weight entries from the sets
KeyedSemElemSet: better printing

I was lazy before, by just printing "<stuff>" for the weight portion. Now I properly iterate over the set associated with the guard. Each set item is clamped in length to make it hopefully more usable.
XFA containment: working again with intermediate version