Remove IXFA_Parser, cleanup XFA parser code.

testing/libfuzzer/pdf_xml_fuzzer.cc

 // Copyright 2016 The PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <cstddef>
 #include <cstdint>
 #include <limits>
 #include <memory>
 
 #include "core/fxcrt/include/fx_basic.h"
 #include "core/fxcrt/include/fx_system.h"
-#include "xfa/fxfa/parser/xfa_parser.h"
 #include "xfa/fxfa/parser/xfa_parser_imp.h"
+#include "xfa/fxfa/parser/xfa_utils.h"
 
 namespace {
 
 CFDE_XMLNode* XFA_FDEExtension_GetDocumentNode(
     CFDE_XMLDoc* pXMLDoc,
     FX_BOOL bVerifyWellFormness = FALSE) {
   if (!pXMLDoc) {
     return nullptr;
   }
   CFDE_XMLNode* pXMLFakeRoot = pXMLDoc->GetRoot();
@@ skipping 37 matching lines @@
   if (!doc->LoadXML(parser.release()))
     return 0;
 
   int32_t load_result = doc->DoLoad(nullptr);
   if (load_result < 100)
     return 0;
 
   (void)XFA_FDEExtension_GetDocumentNode(doc.get());
   return 0;
 }