Remove patch which has been rolled in from libxml2 upstream.

third_party/libxml/src/parser.c

 /*
  * parser.c : an XML 1.0 parser, namespaces and validity support are mostly
  *            implemented on top of the SAX interfaces
  *
  * References:
  *   The XML specification:
  *     http://www.w3.org/TR/REC-xml
  *   Original 1.0 version:
  *     http://www.w3.org/TR/1998/REC-xml-19980210
  *   XML second edition working draft
@@ skipping 8102 matching lines @@
          * ... The declaration of a parameter entity must precede
          * any reference to it...
          */
         if ((ctxt->standalone == 1) ||
             ((ctxt->hasExternalSubset == 0) &&
              (ctxt->hasPErefs == 0))) {
             xmlFatalErrMsgStr(ctxt, XML_ERR_UNDECLARED_ENTITY,
                               "PEReference: %%%s; not found\n",
                               name);
         } else {
-            if ((entity->etype == XML_EXTERNAL_PARAMETER_ENTITY) &&
-                ((ctxt->options & XML_PARSE_NOENT) == 0) &&
-                ((ctxt->options & XML_PARSE_DTDVALID) == 0) &&
-                ((ctxt->options & XML_PARSE_DTDLOAD) == 0) &&
-                ((ctxt->options & XML_PARSE_DTDATTR) == 0) &&
-                (ctxt->replaceEntities == 0) &&
-                (ctxt->validate == 0))
-                return;
             /*
              * [ VC: Entity Declared ]
              * In a document with an external subset or external
              * parameter entities with "standalone='no'", ...
              * ... The declaration of a parameter entity must
              * precede any reference to it...
              */
             xmlWarningMsg(ctxt, XML_WAR_UNDECLARED_ENTITY,
                           "PEReference: %%%s; not found\n",
                           name, NULL);
@@ skipping 7712 matching lines @@
     if (stream == NULL) {
         xmlFreeParserInputBuffer(input);
         return (NULL);
     }
     inputPush(ctxt, stream);
     return (xmlDoRead(ctxt, URL, encoding, options, 1));
 }
 
 #define bottom_parser
 #include "elfgcchack.h"