Add missing operators for CFX_WideString

core/include/fxcrt/fx_string.h

Index: core/include/fxcrt/fx_string.h
diff --git a/core/include/fxcrt/fx_string.h b/core/include/fxcrt/fx_string.h
index df7dd0c76241e359af3e367c400d759a9da9c463..9061c5d90e37b1ee412e0780c5e3edb6e37d3f67 100644
--- a/core/include/fxcrt/fx_string.h
+++ b/core/include/fxcrt/fx_string.h
@@ -7,6 +7,8 @@
 #ifndef _FX_STRING_H_
 #define _FX_STRING_H_
 
+#include <algorithm>
+
 #include "fx_memory.h"
 
 class CFX_ByteStringC;
@@ -702,6 +704,11 @@ public:
 
     const CFX_WideString&	operator += (const CFX_WideStringC& str);
 
+    bool operator< (const CFX_WideString& str) const {
+        int result = wmemcmp(c_str(), str.c_str(), std::min(GetLength(), str.GetLength()));
+        return result < 0 || (result == 0 && GetLength() < str.GetLength());
+    }
+
     FX_WCHAR				GetAt(FX_STRSIZE nIndex) const
     {
         return m_pData ? m_pData->m_String[nIndex] : 0;