Use some FXSYS methods instead of duplicating

xfa/fxfa/parser/cxfa_widgetdata.cpp

 // Copyright 2016 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 "xfa/fxfa/parser/cxfa_widgetdata.h"
 
 #include "core/fxcrt/include/fx_ext.h"
 #include "xfa/fxbarcode/include/BC_Library.h"
@@ skipping 1735 matching lines @@
   if (iCount == 0)
     return wsValue;
 
   int32_t i = 0;
   if (wsValue[i] == L'-') {
     wsRet += L'-';
     i++;
   }
   for (; i < iCount; i++) {
     FX_WCHAR wc = wsValue[i];
-    if (XFA_IsDigit(wc)) {
+    if (FXSYS_isDecimalDigit(wc)) {
       if (iLead >= 0) {
         iLead_++;
         if (iLead_ > iLead)
           return L"0";
       } else if (iTread_ >= 0) {
         iTread_++;
         if (iTread_ > iTread) {
           if (iTread != -1) {
             CFX_Decimal wsDeci = CFX_Decimal(wsValue.AsStringC());
             wsDeci.SetScale(iTread);
             wsRet = wsDeci;
           }
           return wsRet;
         }
       }
     } else if (wc == L'.') {
       iTread_ = 0;
       iLead = -1;
     }
     wsRet += wc;
   }
   return wsRet;
 }