backport changes to make tests work on different architectures

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.00@13575 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
avoid diff options that are not available on BSD

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.00@13576 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02