expose libxml2 xmlIsXHTML on the document object
expose libxml2 xmlIsXHTML on the document object

sferik/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,increments/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,xml4r/libxml-ruby,xml4r/libxml-ruby,increments/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby