bug#41727: 26.3; Doc of `define-minor-mode' and minor-mode commands

[Drew Adams]

For the (default) doc string of a minor mode,
I think something like this should take care of it.

 Interactively, toggle the mode.  But with a prefix arg, enable the
 mode if the numeric value is positive, and disable it otherwise.

 If called from Lisp, toggle the mode if the optional arg is 'toggle'.
 Otherwise, handle it as the prefix arg: disable the mode if
 `prefix-numeric-value' of the arg is non-positive, and enable it
 otherwise.  This implies that if the arg is nil or absent then enable
 the mode.
___

Ideally, we would have a way to provide a custom doc
string that also included this info somehow.

Maybe the doc string of `define-minor-mode' could
show the default doc string and suggest that if you
provide your own doc string you include the same or
similar information, if appropriate.

(And it might generally be good if the Lisp info were
at the end of the doc string.)