Blocked revisions 81196 via svnmerge

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  r81196 | mark.dickinson | 2010-05-15 18:02:38 +0100 (Sat, 15 May 2010) | 13 lines

  Issue #8692: Improve performance of math.factorial:

  (1) use a different algorithm that roughly halves the total number of
      multiplications required and results in more balanced multiplications
  (2) use a lookup table for small arguments
  (3) fast accumulation of products in C integer arithmetic rather than
      PyLong arithmetic when possible.

  Typical speedup, from unscientific testing on a 64-bit laptop, is 4.5x
  to 6.5x for arguments in the range 100 - 10000.

  Patch by Daniel Stutzbach; extensive reviews by Alexander Belopolsky.
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