Match html5 unquoted attribute parsing

Match html5 unquoted attribute parsing

 * Brings us closer to the html5 attribute parsing algorithm described
   in http://www.w3.org/TR/html5/syntax.html#before-attribute-value-state

 * There's a similar patch for the Parsoid in,
   I2160a23b2a3c914eb369347bbf5d58328440041d

 * The spec says <div class=  style="123">hi</div> should parse as
   <div class="style=\"123\"">hi</div>, which it now does, whereas it
   used to yield <div class="" style="123">hi</div>.

 * Merge with caution. This is going to break pages like,
   frwikisource/La_Mirlitantouille_(Lenotre)?oldid=4669681

Bug: T108134
Change-Id: Ic2fc1b573a55a847e6c05707678b58c1189ecc52