Split off CPDF_Document into its own .cpp/.h files.

core/src/fpdfdoc/doc_basic.cpp

 // Copyright 2014 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.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
+#include "core/include/fpdfapi/cpdf_document.h"
 #include "core/include/fpdfdoc/fpdf_doc.h"
 
 const int nMaxRecursion = 32;
 int CPDF_Dest::GetPageIndex(CPDF_Document* pDoc) {
   CPDF_Array* pArray = ToArray(m_pObj);
   if (!pArray)
     return 0;
 
   CPDF_Object* pPage = pArray->GetElementValue(0);
   if (!pPage)
@@ skipping 481 matching lines @@
   int nPage = FXSYS_atoi(bsLbl);
   if (nPage > 0 && nPage <= nPages) {
     return nPage;
   }
   return -1;
 }
 int32_t CPDF_PageLabel::GetPageByLabel(const CFX_WideStringC& wsLabel) const {
   CFX_ByteString bsLabel = PDF_EncodeText(wsLabel.GetPtr());
   return GetPageByLabel(bsLabel);
 }