bpo-29718: Fixed compile on cygwin.

[AraHaan]

Python 3.7 had an issue just like 3.6 with the TLS entries. As such the only way to compile on Cygwin was to replace TLS with TSS. This also fixes issues that was present in the standard library and setup.py in the repo for cygwin as well. TSS is the thing that actually gets python 3.7 to work on cygwin and in fact the only thing currently so TLS is not really used on it at all after this is merged. This will not affect building on MAC, windows, nor even linux at all it will only affect cygwin.

$ ./python.exe
Python 3.7.0a0 (default:4243df51fe43+, Mar  3 2017, 20:14:50)
[GCC 6.3.0] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 

[mention-bot]

@AraHaan, thanks for your PR! By analyzing the history of the files in this pull request, we identified @warsaw, @Haypo, @freddrake, @Yhg1s and @mhammond to be potential reviewers.

[AraHaan]

oops looks like I added an wild -.

[vstinner]

Need more explanation on the reason of the change, let's discuss that on the bug report.

[AraHaan]

Now that I think of it I think having TSS instead of TLS on all platforms if possible would be better sollution so that way cygwin would be unofficially supported until we get build bots for cygwin somehow. The trick is figuring out how to make one similar to the windows (MSVC) build bot.