Support for raise variants in ocamlopt. Only amd64 for now.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/raise_variants@14226 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Cleanup.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/raise_variants@14227 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02