Serhiy: "Is it worth to add other imported libs (libmpdec, libffi)?"

Oh right, I forgot libmpdec: I updated my PR.

By the way, I started a list of embedded libraries:
http://haypo-notes.readthedocs.io/cpython.html#embedded-libraries

* zlib
* expat
* libmpdec
* libffi

libffi should be excluded in Python 2.7 and 3.6, but it was removed from Python 3.7.


Serhiy: "Or may be just remove trailing spaces when import sources from upstream?"

I prefer to leave the copied code unchanged, so it allows to easily cherry-pick from upstream. I did that once for libexpat (for fix a compilation issue on Visual Studio 2008).