[whatwg] "html" start tag token in the root element phase

If the spec dealt with the "html" start tag token directly in the  
root element phase, the parse error in the main phase wouldn't need  
to be conditional. (Implementations that experience a perf benefit  
from not mutating the attributes of a node probably want to hoist the  
"html" node creation to the root element phase for perf reasons, too.)

-- 
Henri Sivonen
hsivonen at iki.fi
http://hsivonen.iki.fi/