[FIX] articles: Work out if article body "is_html" better - test for html in case wysiwyg_htmltowiki has been enabled after wysiwyg has been used for articles before.
Refactor into a new function in artlib and deploy throughout (all tested except received_articles. (thanks Bsfez)
TODO better for 12...

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/11.x@46549 b456876b-0849-0410-b77d-98878d47e9d5