message: Add long long support
diff: @@ -88,6 +88,7 @@ GKO_REGISTER_MPI_TYPE(int, MPI_INT);
  GKO_REGISTER_MPI_TYPE(unsigned short, MPI_UNSIGNED_SHORT);
  GKO_REGISTER_MPI_TYPE(unsigned long, MPI_UNSIGNED_LONG);
  GKO_REGISTER_MPI_TYPE(long, MPI_LONG);
  +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);
  