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_libxml_unparsedEntityDecl(void* user_data, const xmlChar *name,
                                 const xmlChar *publicId, const xmlChar *systemId,
                                 const xmlChar *notationName) {
  raptor_sax2* sax2 = (raptor_sax2*)user_data;
  libxml2_unparsedEntityDecl(sax2->xc, name, publicId, systemId, notationName);
}

raptor_libxml_unparsedEntityDecl(void* user_data, const xmlChar *name,
                                 const xmlChar *publicId, const xmlChar *systemId,
                                 const xmlChar *notationName) {
  raptor_sax2* sax2 = (raptor_sax2*)user_data;
  libxml2_unparsedEntityDecl(sax2->xc, name, publicId, systemId, notationName);
}
