[e-acsl] undefine comparison for derivatives of Misc.Id_term

Make Pred_or_term depend on Misc.Term_id instead of Cil_datatype.Term.
This should have been the case all along, since Pred_or_term is used in
contexts where the physical identity of terms matter. They might be
typed differently depending on contexts (cast or no cast) and thus
require different translations.

Then we undefine the comparison function for both modules which depend
on Misc.Id_term, since there is no meaningful comparison for physical
equality.