remove a special treatement for one-constructor types and add a relevant trigger to the inversion axiom instead
remove a special treatement for one-constructor types
and add a relevant trigger to the inversion axiom instead


ssaavedra/why3,jpdeplaix/why3,douglas-larocca/why3,ssaavedra/why3,jpdeplaix/why3,jpdeplaix/why3,douglas-larocca/why3,ssaavedra/why3,douglas-larocca/why3