(HTMLParser::Text::processEndTag): Clean up
(U16TrivialInputStream::peek): Add a TODO
[HTML] Support document.write (trivial case)

(DocumentImp::write, DocumentImp::writeln): Add more details
(DocumentImp::getInsertionPoint, DocumentImp::setInsertionPoint): New
(HTMLParser::Text::processEndTag): Add more details
(HTMLParser::setInsertionPoint): New
(HTMLTokenizer::insertString): New