Examples: Enable building with the --enable-examples argument to configure

Simple parsing examples:
  dom_parser - Shows how to parse an XML Document with the DOM parser.
  sax_parser - Shows how to parse an XML Document with the SAX parser.

Building XML doxuments:
  dom_build - Shows how to build an XML document using the DOM Parser API.
  sax_parser_build_dom - Shows how to parse an XML document with the SAX parser, building a separate custom DOM as you parse.
  dom_read_write: Reads an XML document with the DOM parser and writes it again. The output should be the same as the input.
  import_node: Adds a part of an XML document to another, using the DOM parser.
  
Entity parsing:
  dom_parser_entities: Shows how to detect entity references when using the DOM parser.
  sax_parser_entities: Shows how to detect (and maybe resolve) entity references when using the SAX Parser.

XPath:
  dom_xpath: Shows how to get XML nodes by specifying them with an XPath, when using the DOM parser.

Others:
  sax_exception: Shows how to implement a libxml++ exception that can be thrown by your SAX parser.
  dom_parser_raw: Test parse_memory_raw() by converting a UTF-8-encoded XML document to UCS-2 and passing the raw memory to the parser.

