HTML::TreeBuilder and XPath compatible interface with libxml

 HTML::TreeBuilder::XPath is libxml based compatible interface
 to HTML::TreeBuilder,
 which could be slow for a large document.
 .
 HTML::TreeBuilder::LibXML is drop-in-replacement
 for HTML::TreeBuilder::XPath.
 .
 This module doesn't implement all of HTML::TreeBuilder
 and HTML::Element APIs,
 but enough methods are defined so modules like Web::Scraper work.