bug#12367: 24.2.50; cl-defun: unused key args are picked up as unused variables

[Stefan Monnier]

>     ;; -*- lexical-binding: t -*-
>     (require 'cl-lib)
>     (cl-defun rms (&key foo))
> Byte compile this piece of code.
>     Warning: Unused lexical variable `foo'

The warning is fine.  But I guess the problem is that the normal fix
(which is to rename `foo' to `_foo') won't work because it forces
callers to use :_foo which is wrong.


        Stefan