Workaround warning

(grafted from 3ffd449ef5
)

unsupported/test/autodiff_scalar.cpp

@@ -81,6 +81,9 @@ void check_limits_specialization()
   typedef std::numeric_limits<AD> A;
   typedef std::numeric_limits<Scalar> B;
 
+  // workaround "unsed typedef" warning:
+  VERIFY(!bool(internal::is_same<B, A>::value));
+
 #if EIGEN_HAS_CXX11
   VERIFY(bool(std::is_base_of<B, A>::value));
 #endif