Attributes/extensions as module types.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13336 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
New syntax:

 Attributes:   ... [@id expr]
 Extension:    [#id expr]
 
 Attributes on items:  ... [@@id expr]




git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13337 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02