Fix order of application of ppx rewriters (matching the order on the command-line).

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14086 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Remove the dump_ast tool.  A better replacement is part of the standalone ppx_tools package.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14087 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02