New package version: PG'OCaml 1.7

This new version of PG'OCaml uses OASIS, which simplifies the build system and removes the need for special patches to work with OPAM.

Also, note that I took the liberty of making myself the maintainer of the OPAM package.  Since I'm also maintaining PG'OCaml and I'm an OPAM user, this should make life easier on everyone.