Blocked revisions 74080 via svnmerge

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  r74080 | mark.dickinson | 2009-07-18 16:18:18 +0100 (Sat, 18 Jul 2009) | 3 lines

  Issue #6431:  Fix Fraction comparisons with unknown types, and with
  float infinities and nans.  Backport of r74078 from py3k.
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