bug#25294: 26.0.50; Allow more catch-all values for cl-defmethod's &context plus major-mode specializer

[Noam Postavsky]

> From: Eric Abrahamsen <eric@ericabrahamsen.net>
> Subject: Re: bug#25294: 26.0.50; Allow more catch-all values for 
> cl-defmethod's &context plus major-mode specializer
> To: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Mon, 11 Dec 2017 16:49:14 -0800 (51 minutes, 9 seconds ago)
>
>> Still not really convinced by this, what's wrong with the last way you
>> put in your OP:
>>
>>     (cl-defmethod example-method ())
>
> A year later, older and wiser, I agree that maybe all that's needed is
> more documentation. I just noticed that, at some point in the interim,
> the documentation for generic functions has been greatly expanded, which
> is nice!
>
> I'd like to add the following to the docs:
>
> 1. The &context thing has to come after the required arguments, but
>    before any &optional or &rest things.
> 2. You can have an arbitrary number of forms following &context.
> 3. The &context arguments don't have to match the declared arguments in
>    `cl-defgeneric'.
> 4. Ergo they can be left off altogether without needing to be
>    specifically declared as nil or what have you, ie, my original bug
>    report isn't really a bug.
>
> If this looks okay, I'll have at the docs.

Sounds good to me.