bug#41884: 27.0.91; `C-h f whitespace-mode' doesn't say that it's a minor mode

[Drew Adams <drew.adams@oracle.com>]

> > > The doc string for a minor mode should tell
> > > you it's a minor mode.
> >
> > Should all minor modes say this?
> 
> No, they don't.

That wasn't Stefan's question.  Should they?
I think they should.

Typically it takes only adding the words "minor
mode".  In the case of `whitespace-mode' it takes
only adding the word "minor":

 Toggle whitespace visualization (Whitespace minor mode).

I can't imagine why we _wouldn't_ want to tell
users this in the doc string.
____

[And, for the related problem that crops up wrt
minor-mode command doc strings - of not always
documenting well how to turn the mode on/off:
if someone decides to opt for a simple one-size
fits all fix, then that could be to just provide
a link to the doc about minor modes in each
minor-mode doc string.

IOW, once every minor-mode doc string says that
it's about a minor mode, a simple link to the doc
that tells you about minor modes would take care
of lacunae such as the doc string neglecting to
tell you clearly how to turn it on/off.

(It's still better to give that info directly in
the doc string, IMO, but such a link would make
sure to cover any such omission.)]