Log Message:
ocaml-findlib: add "stublibs" to base directory set.

This fixes some build problems that have appeared in downstream
packages where libraries that live in the "stublibs" directory don't
get found, e.g. the failure in print/advi that came up this past week.

The problem doesn't affect packages using dune and therefore was
somewhat confusing to sort through.

PKGREVISION -> 1.