improve c++-11 compliance. replace variable size stack allocation.

  double factor = 1.0;

  if (clock_imbalance) factor = clock_imbalance[me];

  double weights[nlocal];

  double *weights = new double[nlocal];

  for (int i = 0; i < nlocal; i++)

    weights[i] = getcost(i)*factor;

  //rcb->compute(dim,atom->nlocal,atom->x,NULL,boxlo,boxhi);

  rcb->compute(dim,atom->nlocal,atom->x,weights,shrinklo,shrinkhi);

  rcb->invert(sortflag);

  delete[] weights;

  // reset RCB lo/hi bounding box to full simulation box as needed