[issue6834] use different mechanism for pythonw on osx: universal builds always run 64-bit on OS X 10.6

[Ned Deily]

Changes by Ned Deily <nad at acm.org>:


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versions: +Python 2.6, Python 3.1

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6834>
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