[Distutils] Installing scripts

[Tim Peters]

"scripts" in the sense we're using here are Python files, and in Windows
they're only useful from "a DOS box".  It's not useful to double-click on
them, it's not useful to have Start menu entries(*) for them, and it would
be hostile to hide them in a hard-to-spell-in-a-DOS-box directory (like
anywhere under the space-ridden "Program Files").

For cross-platform *development*, all Python files should have a .py
extension.  On Windows the extension drives editors and printers too (not
just the "open" action in a DOS box window).

If the build_scripts command wants to strip .py extensions on non-Windows
boxes, that's fine by me.  I'm happy enough with where they end up on
Windows now, and delighted there are no Start menu entries for them, it's
just the lack of the natural (on Windows) .py extension that creates
needless pain (on Windows).


(*) The only thing useful to have in the Start menu is a program
    that supplies its own GUI, or a program that has no UI.  On Windows,
    that's what the .pyw extension is for (brings up Python without
    "a DOS box", so there's no UI at all unless the script supplies
    its own UI; for example, IDLE supplies its own UI, via Tk).