[docs] [issue20699] Document that binary IO classes work with bytes-likes objects

[Martin Panter]

Martin Panter added the comment:

Posting bytes-like-param.v4.patch, with David’s suggested wording

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Added file: http://bugs.python.org/file38207/bytes-like-param.v4.patch

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<http://bugs.python.org/issue20699>
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