[docs] Bring Doc/using/windows up to date (issue 20265)

[martin at v.loewis.de]

http://bugs.python.org/review/20265/diff/11405/Doc/using/windows.rst
File Doc/using/windows.rst (right):

http://bugs.python.org/review/20265/diff/11405/Doc/using/windows.rst#newcode104
Doc/using/windows.rst:104: Python 3.4, the installer has an option to
set that up for you.
It's actually available since 3.3.

http://bugs.python.org/review/20265/diff/11405/Doc/using/windows.rst#newcode106
Doc/using/windows.rst:106: At the "Customize Python 3.3" screen, an
option called
If you want to update the version number, this would be the place.

http://bugs.python.org/review/20265/diff/11405/Doc/using/windows.rst#newcode175
Doc/using/windows.rst:175: Executing scripts without the Python launcher
Why do we need this section? It's not possibly anymore to not install
the Python launcher. The use case of binding .py to the no-console
executable might be useful, but then the executable is pyw.exe, not
pythonw.exe.

There *could* be a use case of binding .py to a specific version,
however, I'd rather suggest to use launcher syntax in the script (e.g.
#!python3.3) to achieve that.

http://bugs.python.org/review/20265/diff/11405/Doc/using/windows.rst#newcode193
Doc/using/windows.rst:193: assoc .py=Python.File
Hmm. In the standard installation, .py is already associated with
Python.File, so this step is unnecessary. If the objective is to
associate .py with pythonw.exe, I'd rather do

assoc .py=Python.NoConFile

and not change the Open path for Python.File at all. But maybe I'm
missing something.

http://bugs.python.org/review/20265/