Windows: Make "multiprocessing" plugin more robust.
Windows: Make "multiprocessing" plugin more robust.

* It could happen that patching the forking pickler didn't happen,
  depending on import visiblity.

* This moves the monkey patching to after loading multiprocessing
  module, making sure it always happens.

kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka