Merged revisions 78384 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r78384 | dirkjan.ochtman | 2010-02-23 16:09:52 -0500 (Tue, 23 Feb 2010) | 4 lines

  Fix #1537721: add writeheader() method to csv.DictWriter.

  Reviewed by skip.montanaro and thomas.wouters.
........