Goal:
    x : VSet.elt  p : VSet.t  H : ~ VSet.In x p
  ============================
   (VSet.Equal (VSet.remove x (VSet.add x p)) p)


DEBUG:Going to execute:
auto  100 with MSet_Prop
DEBUG LTAC Evaluated term: (VSetDecide.MSetDecideAuxiliary.MSet_Prop
                              (~ VSet.In x p))