Message 110033 - Python tracker

* hardcoded deafult PATHEXT values for different versions of Windows
  (confirmed the W2K, W2008 values via google)
* code+tests+docs cleanup

Just one question: is there some std proc how to run the test suite on the updated stdlib in a working repo?
For now, I just copied the Lib/test/test_shutil.py to a parent Lib/ dir, renamed Lib/test temporarily to not collide with a test module, and run python test_shutil.py in Lib, but I guess you have some simpler way to do it.