fix linking problems due to MSVC implicitly considering template classes specializations used as base classes DLL-exported even though it doesn't actually export them when building the DLL (with or without explicit declspec(dllexport)); also replace wxCharTypeBuffer::NullData with a static function to allow not DLL-exporting this class

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56602 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/ustring.cpp

@@ -542,16 +542,3 @@ wxU16CharBuffer wxUString::utf16_str() const
     
     return result;    
 }
-
-
-#if SIZEOF_WCHAR_T != 2
-template<>
-wxCharTypeBuffer<wxChar16>::Data
-wxCharTypeBuffer<wxChar16>::NullData(NULL);
-#endif
-
-#if SIZEOF_WCHAR_T != 4
-template<>
-wxCharTypeBuffer<wxChar32>::Data
-wxCharTypeBuffer<wxChar32>::NullData(NULL);
-#endif