bug#2941: rmail's new handling of Babyl files is odd

[Richard M Stallman]

    It fixes the above sequence; however I can still go from Babyl to mbox
    with no prompting by doing:

    C-u M-x rmail RET foo RET
    d
    x
    y

I think that y is the answer to a prompt.

It is a feature that rmail-expunge-confirm avoids prompting twice.
If it prompts you about whether to expunge at all, it doesn't
prompt a second time about the change in format.

Of course, this can be changed if people prefer.