bug#29081: 25.1; define-globalized-minor-mode does not respect :variable of original mode

[k@rdw.se (Chris Stj)]

I tried to define a global version of auto-fill mode by evaluating

  (define-globalized-minor-mode global-auto-fill-mode auto-fill-mode
    turn-on-auto-fill)

The problem is that when the define-globalized-minor-mode macro expands,
it defines the function

       (defun ,MODE-enable-in-buffers ()
	 (dolist (buf ,MODE-buffers)
	   (when (buffer-live-p buf)
	     (with-current-buffer buf
               (unless ,MODE-set-explicitly
		 (unless (eq ,MODE-major-mode major-mode)
		   (if ,mode
		       (progn
			 (,mode -1)
			 (funcall #',turn-on))
		     (funcall #',turn-on))))
	       (setq ,MODE-major-mode major-mode)))))

The problem lies in the "if ,mode" condition. This assumes the minor
mode variable has the same name as the minor mode itself; which is
clearly not true when something else is specified with the :variable
keyword in the minor mode definition.

I noticed this with auto-fill-mode, since it calls its status variable
auto-fill-function rather than auto-fill-mode.

I guess the best solution may be to allow users of
define-globalized-minor-mode to specify the place in which the minor
mode stores its state, since I can't find a good, generic way to extract
this from the minor mode definition itself, after the fact.

Regards,
Chris