Fusion: silenced a couple of MSVC warnings created during Spirit test runs

[SVN r57502]

include/boost/fusion/adapted/struct/struct_iterator.hpp

@@ -95,6 +95,10 @@ namespace boost { namespace fusion
                 return type();
             }
         };
+
+    private:
+        // silence MSVC warning C4512: assignment operator could not be generated
+        struct_iterator& operator= (struct_iterator const&);
     };
 }}