bug#12460: 24.2.50; toggling read-only interactively: echo new state

[Drew Adams]

> > And since you've now made `toggle-read-only' obsolete (though it is
> > still invoked by `C-x C-q' - see bug #12462), please make
> > `read-only-mode' echo the new state as well.  It too should provide
> > a Boolean arg or equivalent to control the display of the new-state
> > message from Lisp.
> 
> All minor modes follow the same rule and use `called-interactively-p'
> rather than an extra argument.  So if we want to change it it's in
> easy-mmode.el and will apply to all minor modes.

I see.  And I see that `read-only-mode' already does echo the new state when
invoked interactively.  I guess this can be closed - I'll do that.  But please
update the doc (bug #12462).