fix invalid printf formats

There are some format strings that are "invalid" in the coccinelle sources.

In general, invalid formats are nonsensical format strings that were accepted in OCaml 4.01.0 and earlier, but whose semantics is unspecified. They are still accepted by the new Printf implementation of OCaml 4.02.0 but in some cases with different semantics, and they will be statically rejected by OCaml 4.03.0.

You can check for them in OCaml 4.02.0 with the flag -strict-formats.

In the case of coccinelle, I think the behavior has not changed between 4.01.0 and 4.02.0, but you should take the opportunity to review the formats in question.