Blocked revisions 68789,68792 via svnmerge

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  r68789 | raymond.hettinger | 2009-01-19 19:19:26 -0600 (Mon, 19 Jan 2009) | 6 lines

  Build-outs for Counter() class:
  * Constructor and update() support keyword args (like their dict counterparts).
  * The 'del' statement no longer raises KeyError for missing values.
  * Add multiset operations:  __add__, __sub__, __and__, __or__.
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  r68792 | raymond.hettinger | 2009-01-19 20:24:38 -0600 (Mon, 19 Jan 2009) | 1 line

  Add Counter() to __all__.
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