ocaml ports: libraries built with one ocaml version fail on later ones

[pmetzger (Perry E. Metzger)]

For most OCaml ports, there's a problem, which is that library binaries built with OCaml will not be compatible with binaries compiled by subsequent versions of the compiler.

A kludgy way to do this is probably to update "revision" for every ocaml port, but there are a lot of them, and this seems like an inefficient use of human labor. For now, though, that might be the best available mechanism.