Functions that take 'r' type arguments will fail if given an argument
that is a name defined to be a single cell.  OFFSET is such a function.

We have special code for the case where the single cell is given directly
as an argument so that works ok.

  1250  if (arg_type == 'A' || arg_type == 'r') {
  1251          if (GNM_EXPR_GET_OPER (expr) == GNM_EXPR_OP_CELLREF) {
>>>SPECIAL CASE
  1252                  GnmCellRef r;
  1253                  gnm_cellref_make_abs (&r, &expr->cellref.ref, ei->pos);
  1254                  args[i] = value_new_cellrange_unsafe (&r, &r);
  1255          } else {
  1256                  tmp = args[i] = gnm_expr_eval (expr, ei->pos,
  1257                          GNM_EXPR_EVAL_PERMIT_NON_SCALAR);
>>>SINGLE CELL WILL PRODUCE A (DEREFERENCED) VALUE
  1258                  if (tmp->type == VALUE_CELLRANGE) {
  1259                          gnm_cellref_make_abs (&tmp->v_ra