Fix -Woverloaded-virtual warnings in ICU.

source/i18n/winnmfmt.h

 /*
 ********************************************************************************
 *   Copyright (C) 2005-2014, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 ********************************************************************************
 *
 * File WINNMFMT.H
 *
 ********************************************************************************
 */
@@ skipping 125 matching lines @@
      * compilers support genuine RTTI. Polymorphic operator==() and clone()
      * methods call this method.
      *
      * @return          The class ID for this object. All objects of a
      *                  given class have the same class ID.  Objects of
      *                  other classes have different class IDs.
      */
     virtual UClassID getDynamicClassID(void) const;
 
 private:
-    UnicodeString &format(int32_t numDigits, UnicodeString &appendTo, const wchar_t *format, ...) const;
+    UnicodeString &variadicFormat(int32_t numDigits, UnicodeString &appendTo, const wchar_t *format, ...) const;
 
     UBool fCurrency;
     Locale fLocale;
     int32_t fLCID;
     FormatInfo *fFormatInfo;
     UBool fFractionDigitsSet;
 
 };
 
 U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 #endif // U_PLATFORM_USES_ONLY_WIN32_API
 
 #endif // __WINNMFMT