For libxml2.

 DOCTYPE comes out as a tag with the top-level tag name (e.g. dataset in
mtcars.xml)
 Can we distinguish it.


 Reading raw.xml doesn't work.


 XML_ENTITY_DECL in createXMLNode needs to be handled carefully.

 test.xml causes problems because of definition of entity referring
 to an entity.

> parseDTD("data/foo.dtd")
  Error in parseDTD("data/foo.dtd") : error in DTD data/foo.dtd


In libxml1.8.9, the processing instructions in raw.xml are not displayed.
 It is in the value section.