[cgiow] (3) Change how dir='' works, from being an embedding to being an override, for better results on mixed-directionality sites. Fixes W3C HTML5 CR bug 22326: https://www.w3.org/Bugs/Public/show_bug.cgi?id=22326

git-svn-id: http://svn.whatwg.org/webapps@8283 340c8d12-0b0e-0410-8428-c7bf67bfef74
(cherry picked from commit a43f5fb21c05c159be980c9567bcaa59a49308f1)
(cherry picked from commit cf3f3dbbc3a28e0b6f82d6395427c84b4bf489a8)