[issue29688] Add support for Path.absolute()

[INADA Naoki]

INADA Naoki added the comment:

> posixpath.abspath() collapses "<path>/<symlink>/.." to "<path>", this is not correct. Not sure about ntpath.abspath().

I feel this is reasonable limitation, and expected behavior for some cases.
So I think adding note about this in document is enough.

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nosy: +inada.naoki

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29688>
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