Flattenize Mem operand.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/abstract_intel_emit@15280 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Simplify addressing.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/abstract_intel_emit@15281 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02