Can't disable buffering on std streams in Python 3.

Breakthrough! If I set PYTHONPATH weirdly, I can now start make.py in a directory without a Makefile.

    $ set PYTHONPATH=%PWD%;%PWD%\pymake
    $ which python
    C:\Python33\python.EXE
    $ python make.py
    make.py[0]: Entering directory 'D:\dev\pymake'
    No makefile found
    $

There are still a few ``xrange`` calls in there, that's my next target. Then I'll probably need some help with untangling dependencies so I can start packaging.
The unbuffered output is important: without it, the output can get lost, apparently. See https://bugzilla.mozilla.org/show_bug.cgi?id=794490