Allow a binary code emitter to avoid the creation of an assembly source file.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/abstract_intel_emit@15187 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Let the binary backend split the sections.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/abstract_intel_emit@15188 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02