bug#24520: 25.1.50; calccard.tex has somewhat unclear licensing

[Glenn Morris]

Richard Stallman wrote:

> The original reference card says this:
>
>     Permission is granted to make and distribute modified or unmodified
>     copies of this card provided the copyright notice and this permission
>     notice are preserved on all copies.
>
> But some other reference cards, including dired-ref.tex also,
> say this:
>
>   > > > > Permission is granted to make and distribute copies of
>   > > > > this card provided the copyright notice and this permission notice
>   > > > > are preserved on all copies.

refcard.tex used to say what dired-ref says, until:

2007-08-22  Karl Berry  <karl@gnu.org>

            * refcards/refcard.tex: Updates for printing.
            (\versionyear): Update to 2007.
            (\copyrightnotice): Modify or unmodified ok.

(IMO the a,b,c suggestions in the original report are all good.)