[giow] (1) Move all requirements about bidi out and just rely on CSS instead. Also, fix the CSS rules for <bdo>.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23260
Affected topics: HTML, Rendering

git-svn-id: http://svn.whatwg.org/webapps@8317 340c8d12-0b0e-0410-8428-c7bf67bfef74
(cherry picked from commit f397c78de13607ff21d27e112e4663447672a409)