grid_duplicate_lines
grid_duplicate_lines(s->saved_grid, 0, s->grid, screen_hsize(s), sy);
grid_duplicate_lines(s->grid, screen_hsize(s), s->saved_grid, 0,
void grid_duplicate_lines(struct grid *, u_int, struct grid *, u_int,
grid_duplicate_lines(dst->grid, 0, src->grid, 0, sy);