Allow abstract module declaration in structures to make the syntax and Parsetree more uniform.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13556 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Another simple ppx extension which allows to include type/module type definitions from external .ml/mli files (by default, from the .mli file corresponding to the current .ml file).

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13562 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Cleanup.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/extension_points@13564 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02