Some more helper functions.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14081 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Move some tools to a dedicated external project (https://github.com/alainfrisch/ppx_tools).

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14082 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02