Function swap

Libs/flatbuffers/flatbuffers.h:1137–1147

  void scratch_pop(size_t bytes_to_remove) { scratch_ -= bytes_to_remove; }

  void swap(vector_downward &other) {
    using std::swap;
    swap(allocator_, other.allocator_);
    swap(own_allocator_, other.own_allocator_);
    swap(initial_size_, other.initial_size_);
    swap(buffer_minalign_, other.buffer_minalign_);
    swap(reserved_, other.reserved_);
    swap(buf_, other.buf_);
    swap(cur_, other.cur_);
    swap(scratch_, other.scratch_);
  }

  void swap_allocator(vector_downward &other) {
    using std::swap;