Manage face-remapping-alist properly in face-remap-add-relative.

* face-remap.el (face-remap-add-relative): Handle the case where a
face-remapping-alist entry is a cons cell.

Fixes: debbugs:12762

lisp/ChangeLog

+2012-10-29  Chong Yidong  <cyd@gnu.org>
+
+	* face-remap.el (face-remap-add-relative): Handle the case where a
+	face-remapping-alist entry is a cons cell (Bug#12762).
+
 2012-10-29  Glenn Morris  <rgm@gnu.org>
 	* emacs-lisp/cl.el (defsetf): Doc fix.

lisp/face-remap.el

@@ -132,7 +132,10 @@ other than the normal definition of FACE via `face-remap-set-base'."
     (when (null entry)
       (setq entry (list face face))	; explicitly merge with global def
       (push entry face-remapping-alist))
-    (setcdr entry (face-remap-order (cons specs (cdr entry))))
+    (let ((faces (cdr entry)))
+      (if (symbolp faces)
+	  (setq faces (list faces)))
+      (setcdr entry (face-remap-order (cons specs faces))))
     (cons face specs)))
 
 (defun face-remap-remove-relative (cookie)