Blocked revisions 76295 via svnmerge

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  r76295 | mark.dickinson | 2009-11-15 12:31:13 +0000 (Sun, 15 Nov 2009) | 5 lines

  Avoid signed overflow in some xrange calculations, and extend
  xrange tests to cover some special cases that caused problems
  in py3k.  This is a partial backport of r76292-76293 (see
  issue #7298.)
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