(protected) r = this << n*DB
function bnpDLShiftTo(n,r) {
  var this_array = this.array;
  var r_array = r.array;
  var i;
  for(i = this.t-1; i >= 0; --i) r_array[i+n] = this_array[i];
  for(i = n-1; i >= 0; --i) r_array[i] = 0;
  r.t = this.t+n;
  r.s = this.s;
}