Rename copy_reg module to copyreg.

Rename copy_reg module to copyreg.
Updated documentation.
Merged revisions 63042 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r63042 | alexandre.vassalotti | 2008-05-11 04:25:28 -0400 (Sun, 11 May 2008) | 5 lines

  Added module stub for copy_reg renaming in 3.0.
  Renamed copy_reg to copyreg in the standard library, to avoid
  spurious warnings and ease later merging to py3k branch. Public
  documentation remains intact.
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