Attributes on exception declarations.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13342 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Attributes on open/include in signatures.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13343 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02