Add missing operators for CFX_ByteString.

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..023f383208593bbed45726d07f40c1e756dd85de 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;
@@ -261,6 +263,12 @@ public:
         return !operator==(str);
     }
 
+    bool operator< (const CFX_ByteString& str) const
+    {
+        int result = FXSYS_memcmp32(c_str(), str.c_str(), std::min(GetLength(), str.GetLength()));
+        return result < 0 || (result == 0 && GetLength() < str.GetLength());
+    }
+
     void					Empty();
 
     const CFX_ByteString&	operator = (FX_LPCSTR str);