Backport http://dev.plone.org/archetypes/changeset/11766/Products.PortalTransforms/trunk/Products/PortalTransforms/transforms/safe_html.py
- add support of HTML5


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36537 20353a03-c40f-0410-a6d1-a30d3c3de9de