Add patches to build Pythons 2.7 through 3.5 on Cygwin

[embray]

This is some initial work to support building supported Python 3 versions on Cygwin. Although Python 2.7 already works on Cygwin, Python 3.2 and up require either updated or additional patches.

These Python 3 builds can't be said to be 100% working since they don't pass all the tests. Some of that is issues with the tests themselves though (I have personally been working on a set of patches to cpython to get Cygwin support up to speed again, and may include some of those her later).

The ugly repetitious nature of this motivates #979 which might be nice to have first.

[embray]

This needs some work--I'm still getting a build failure at least on Python 3.4 (will try other versions too). At the end of the make run it dies with:

2016/12/07 11:23:48 - INFO: [package:run_job] export PATH; PATH="`pwd`:$PATH"; \
2016/12/07 11:23:48 - INFO: [package:run_job] export PYTHONPATH; PYTHONPATH="`pwd`/Lib"; \
2016/12/07 11:23:48 - INFO: [package:run_job] export DYLD_FRAMEWORK_PATH; DYLD_FRAMEWORK_PATH="`pwd`"; \
2016/12/07 11:23:48 - INFO: [package:run_job] export EXE; EXE=".exe"; \
2016/12/07 11:23:48 - INFO: [package:run_job] if [ -n "" ]; then export MULTIARCH; MULTIARCH=; fi; \
2016/12/07 11:23:48 - INFO: [package:run_job] export PYTHON_FOR_BUILD; \
2016/12/07 11:23:48 - INFO: [package:run_job] if [ "x86_64-unknown-cygwin" = "x86_64-unknown-cygwin" ]; then \
2016/12/07 11:23:48 - INFO: [package:run_job]   PYTHON_FOR_BUILD="python.exe"; \
2016/12/07 11:23:48 - INFO: [package:run_job] else \
2016/12/07 11:23:48 - INFO: [package:run_job]   PYTHON_FOR_BUILD="./python.exe -E"; \
2016/12/07 11:23:48 - INFO: [package:run_job] fi; \
2016/12/07 11:23:48 - INFO: [package:run_job] cd ./Lib/plat-cygwin;  ./regen
2016/12/07 11:23:48 - INFO: [package:run_job] eval $PYTHON_FOR_BUILD ../../Tools/scripts/h2py.py -i "'(u_long)'" /usr/include/netinet/in.h
2016/12/07 11:23:48 - INFO: [package:run_job] python.exe ../../Tools/scripts/h2py.py -i '(u_long)' /usr/include/netinet/in.h
2016/12/07 11:23:48 - INFO: [package:run_job] Could not find platform independent libraries <prefix>
2016/12/07 11:23:48 - INFO: [package:run_job] Could not find platform dependent libraries <exec_prefix>
2016/12/07 11:23:48 - INFO: [package:run_job] Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
2016/12/07 11:23:48 - INFO: [package:run_job] Failed to import the site module
2016/12/07 11:23:48 - INFO: [package:run_job] Traceback (most recent call last):
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/site.py", line 562, in <module>
2016/12/07 11:23:48 - INFO: [package:run_job]     main()
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/site.py", line 548, in main
2016/12/07 11:23:48 - INFO: [package:run_job]     known_paths = addusersitepackages(known_paths)
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/site.py", line 281, in addusersitepackages
2016/12/07 11:23:48 - INFO: [package:run_job]     user_site = getusersitepackages()
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/site.py", line 257, in getusersitepackages
2016/12/07 11:23:48 - INFO: [package:run_job]     user_base = getuserbase() # this will also set USER_BASE
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/site.py", line 247, in getuserbase
2016/12/07 11:23:48 - INFO: [package:run_job]     USER_BASE = get_config_var('userbase')
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/sysconfig.py", line 589, in get_config_var
2016/12/07 11:23:48 - INFO: [package:run_job]     return get_config_vars().get(name)
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/sysconfig.py", line 538, in get_config_vars
2016/12/07 11:23:48 - INFO: [package:run_job]     _init_posix(_CONFIG_VARS)
2016/12/07 11:23:48 - INFO: [package:run_job]   File "/home/embray/.hashdist/tmp/python-6me5wi3b4usz-1/Lib/sysconfig.py", line 410, in _init_posix
2016/12/07 11:23:48 - INFO: [package:run_job]     from _sysconfigdata import build_time_vars
2016/12/07 11:23:48 - INFO: [package:run_job] ImportError: No module named '_sysconfigdata'
2016/12/07 11:23:48 - INFO: [package:run_job] make: *** [Makefile:1281: Lib/plat-cygwin] Error 1

When I manually cd into the build directory and run make again it succeeds, so I don't know if it's something strange about the environment hashdist is setting up or what.