Define traits::is_view for non fusion types

test/sequence/adapt_assoc_struct_named.cpp

@@ -66,6 +66,7 @@ main()
 
     {
         BOOST_MPL_ASSERT((traits::is_view<adapted::point>));
+        BOOST_STATIC_ASSERT(traits::is_view<adapted::point>::value);
         ns::point basep = {123, 456};
         adapted::point p(basep);