bpo-24643: Fix "#define timezone _timezone" clashes on Windows

[ZackerySpytz]

Several solutions were proposed on the bug tracker.

https://bugs.python.org/issue24643

[miss-islington]

Thanks @ZackerySpytz for the PR, and @zooba for merging it 🌮🎉.. I'm working now to backport this PR to: 3.7.
🐍🍒⛏🤖

[bedevere-bot]

GH-12040 is a backport of this pull request to the 3.7 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x Debian 3.x has failed when building commit 6673dec.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/13/builds/2414) and take a look at the build logs.
4. Check if the failure is related to this commit (6673dec) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/13/builds/2414

Click to see traceback logs

Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-debian-z/build/Lib/test/_test_multiprocessing.py", line 2754, in test_mymanager_context_prestarted
    self.assertEqual(manager._process.exitcode, 0)
AssertionError: -11 != 0

----------------------------------------------------------------------

Ran 344 tests in 101.444s

FAILED (failures=1, skipped=32)


Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-debian-z/build/Lib/test/test_descr.py", line 4341, in test_vicious_descriptor_nonsense
    self.assertEqual(c.attr, 1)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-debian-z/build/Lib/test/test_descr.py", line 4328, in __eq__
    del C.attr
AttributeError: attr

----------------------------------------------------------------------

Ran 140 tests in 1.368s

FAILED (errors=1, expected failures=2)


Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-debian-z/build/Lib/test/test_descr.py", line 4341, in test_vicious_descriptor_nonsense
    self.assertEqual(c.attr, 1)
  File "/home/dje/cpython-buildarea/3.x.edelsohn-debian-z/build/Lib/test/test_descr.py", line 4328, in __eq__
    del C.attr
AttributeError: attr

----------------------------------------------------------------------

Ran 140 tests in 1.567s

FAILED (errors=1, expected failures=2)