message: Use CXX MPI datatypes
diff: @@ -116,8 +116,8 @@ GKO_REGISTER_MPI_TYPE(long long, MPI_LONG_LONG_INT);
  GKO_REGISTER_MPI_TYPE(float, MPI_FLOAT);
  GKO_REGISTER_MPI_TYPE(double, MPI_DOUBLE);
  GKO_REGISTER_MPI_TYPE(long double, MPI_LONG_DOUBLE);
  -GKO_REGISTER_MPI_TYPE(std::complex<float>, MPI_C_COMPLEX);
  -GKO_REGISTER_MPI_TYPE(std::complex<double>, MPI_C_DOUBLE_COMPLEX);
  +GKO_REGISTER_MPI_TYPE(std::complex<float>, MPI_CXX_FLOAT_COMPLEX);
  +GKO_REGISTER_MPI_TYPE(std::complex<double>, MPI_CXX_DOUBLE_COMPLEX);
  /**
  