Move the cmxs rule to Before_rules
Move the cmxs rule to Before_rules

Ignore-this: 2961f08497b0bc108cf700a75ed3d410

Move the cmxs rule to Before_rules, so that it overrides the built-in
rules (which are present in OCaml 3.12).

darcs-hash:20100429054323-0445d-bb2fb347825525f5e26a0271d1cfd9414e9396a0

diml/ocaml-usb,diml/ocaml-usb