cast(): use cast_op_type mechanism

include/pybind11/cast.h

@@ -764,10 +764,11 @@ public:
 NAMESPACE_END(detail)
 
 template <typename T> inline T cast(handle handle) {
-    detail::type_caster<typename detail::intrinsic_type<T>::type> conv;
+    typedef detail::type_caster<typename detail::intrinsic_type<T>::type> type_caster;
+    type_caster conv;
     if (!conv.load(handle, true))
         throw cast_error("Unable to cast Python object to C++ type");
-    return (T) conv;
+    return conv.operator typename type_caster::template cast_op_type<T>();
 }
 
 template <typename T> inline object cast(const T &value, return_value_policy policy = return_value_policy::automatic_reference, handle parent = handle()) {