bug#20517: define-modify-macro: void function: cl--arglist-args

[Stefan Monnier]

> Byte-compiling the following works fine in Emacs 24.2, but in 24.3
> and later it fails with:

>   foo.el:3:1:Error: Symbol's function definition is void: cl--arglist-args

> ;; foo.el:
> (eval-when-compile (require 'cl))
> (define-modify-macro foo (&optional (n 1)) +)

Looks like I messed up this part when switching to gv.el.
But since noone noticed until now, I guess we should simply remove
define-modify-macro.


        Stefan