Log Message:
Updated package to latest version, 4.0. Changes include:

  Show, eq, ord, map, iter, fold: add support for Result.result.
  Ppx_deriving.Arg: use Result.result instead of polymorphic variants.
  Ppx_deriving.sanitize: parameterize over an opened module.
  Add support for [@@deriving] in module type declarations.
  Add support for loading findlib packages instead of just files in \ 
ppx_deriving_main.
  Treat types explicitly qualified with Pervasives also as builtin.
  Compatibility with statically linked ppx drivers.