Extracted from revision a1daf2d289ad by Zachary Ware.

ctypes.CDLL instances.

KeyError could be raised when cached function with full cache was
simultaneously called from differen threads with the same uncached arguments.

Windows requires at least the SYSTEMROOT environment variable to start Python.
If run_python_until_end() doesn't copy SYSTEMROOT, the function always fail on
Windows.

Based on patch by Martin Panter.

  - There was no real problem to begin with.

  - The hypothetical problem has been fixed by 5bdc8e1a50c8.

Copy and then adapt Python/random.c from default branch. Difference between 3.5
and default branches:

* Python 3.5 only uses getrandom() in non-blocking mode: flags=GRND_NONBLOCK
* If getrandom() fails with EAGAIN: py_getrandom() immediately fails and
  remembers that getrandom() doesn't work.
* Python 3.5 has no _PyOS_URandomNonblock() function: _PyOS_URandom()
  works in non-blocking mode on Python 3.5

In urllib.request, suffixes in no_proxy environment variable with
leading dots could match related hostnames again (e.g. .b.c matches a.b.c).
Patch by Milan Oberkirch.

test_powlong is the same as test_powint.
Patch by Lukas Schwaighofer.

Noticed by Serhiy Storchaka.

Patch by Jim Fasarakis-Hilliard.