Merged revisions 82646,82649-82650 via svnmerge from

Merged revisions 82646,82649-82650 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r82646 | mark.dickinson | 2010-07-08 18:23:40 +0100 (Thu, 08 Jul 2010) | 1 line

  In test_decimal, convert heuristic for skipping tests into an explicit skiplist.
........
  r82649 | mark.dickinson | 2010-07-08 20:03:34 +0100 (Thu, 08 Jul 2010) | 1 line

  Fix a performance issue in Decimal.pow.  Thanks Stefan Krah for finding this.
........
  r82650 | mark.dickinson | 2010-07-08 20:09:16 +0100 (Thu, 08 Jul 2010) | 1 line

  Fix misplaced exactness check that was causing unnecessary work in Decimal.__pow__.
........