task views are now generated as strict XHTML
hence target="_top" is not allowed anymore


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/ctv@1896 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
also avoid using target within ctv2html, e.g., for BioC URLs etc.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/ctv@1897 edb9625f-4e0d-4859-8d74-9fd3b1da38cb