CVE-2012-0037

Enforce entity loading policy in raptor_libxml_resolveEntity
and raptor_libxml_getEntity by checking for file URIs and network URIs.

Add RAPTOR_OPTION_LOAD_EXTERNAL_ENTITIES / loadExternalEntities for
turning on loading of XML external entity loading, disabled by default.

This affects all the parsers that use SAX2: rdfxml, rss-tag-soup (and
aliases) and rdfa.
raptor_rdfxml_characters_handler(void *user_data, 
                                 raptor_xml_element* xml_element,
                                 const unsigned char *s, int len)
{
  raptor_parser* rdf_parser = (raptor_parser*)user_data;

  raptor_rdfxml_cdata_grammar(rdf_parser, s, len, 0);
}

raptor_rdfxml_characters_handler(void *user_data, 
                                 raptor_xml_element* xml_element,
                                 const unsigned char *s, int len)
{
  raptor_parser* rdf_parser = (raptor_parser*)user_data;

  raptor_rdfxml_cdata_grammar(rdf_parser, s, len, 0);
}
