adjust_markers
void adjust_markers(mark_pointer low, mark_pointer high,
adjust_markers (pos << 1, size1() << 1, gap_size(), data);
adjust_markers ((size1() + gap_size()) << 1, (pos + gap_size()) << 1,
adjust_markers (s1 << 1, (buf_size << 1) + 1, k, old_data);
adjust_markers ((to + gap_size()) << 1, (to + gap_size()) << 1,