bug#47813: 28.0.50; Confusing new calling convention for define-minor-mode

[Stefan Monnier]

> says that the convention as printed is not valid - and indeed it
> isn't -- e.g. this errors:
>
>   (define-minor-mode test-mode "..." (if test-mode 17 23))
>
> Is it possible to make that keyword-less case work?

It's hard to do it as long as there is code out there that uses the old
convention where the first element of "body" is actually interpreted as
the `lighter` argument.

That's why I introduced the warning and changed the arglist: I realized
that even though I think the old convention is inconvenient and
confusing, it seems that a lot of code (even brand new code) follows the
new rather than the old convention, so we need to be more proactive to
get people to abandon the old convention so we can at some point in the
future accept code like the one above.


        Stefan