Coq: put a commented "intros" line before old proofs
Coq: put a commented "intros" line before old proofs

unless the old proof already starts with "(* intros "

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