According to rfc, (http://tools.ietf.org/html/rfc2046#section-5.1.4)
  getTextContent should return html part of multipart/alternative couple
  If multipart/mixed, the html part is an attachementi not the message. So return the
  main content (best match in multipart/alternative couple).


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@34397 20353a03-c40f-0410-a6d1-a30d3c3de9de