message: Fix stack overflow on gcc with c++17
diff: @@ -1809,7 +1809,7 @@ Mat_<_Tp> Mat_<_Tp>::cross(const Mat_& m) const
  template<typename _Tp> template<typename T2> inline
  Mat_<_Tp>::operator Mat_<T2>() const
  {
  - return Mat_<T2>(*this);
  + return Mat_<T2>(static_cast<const Mat&>(*this));
  }
  template<typename _Tp> inline
  