bug#122: 23.0.60; Slowdown in directory scanning over time.

[Richard M. Stallman]

    > The code looks inefficient too.  Even when it reuses the
    > code-conversion buffer, it calls Fget_buffer_create.
    > It seems to be killing and recreating these buffers,
    > which must be slow.

    ???  I don't see what's wrong with the current code.  I
    think the functions make_conversion_work_buffer,
    code_conversion_save, and code_conversion_restore do the
    right thing.

They do the right thing, but it looks like they do it inefficiently.

Whether that is a significant slowdown, I do not know.