message: Add const OperatorHandle::operator*
diff: @@ -87,6 +87,9 @@ public:
  /// Access the underlying Operator.
  Operator &operator*() { return *oper; }
  + /// Access the underlying Operator.
  + const Operator &operator*() const { return *oper; }
  +
  /// Get the currently set operator type id.
  Operator::Type Type() const { return type_id; }
  