Fix C-M-x on defcustoms

[Jambunathan K]

1. M-x find-library RET vc-dir.el
2. C-s defcustom
3. C-M-x.  Note the following backtrace.

,----
| Debugger entered--Lisp error: (invalid-function (\, (lambda nil nil)))
|   (\, (lambda nil nil))()
|   funcall((\, (lambda nil nil)))
|   eval((funcall (function (\, (lambda nil nil)))) t)
|   eval-defun-1((custom-declare-variable (quote vc-dir-mode-hook) (\` (funcall 
(function (\, (lambda nil nil))))) "Normal hook run by `vc-dir-mode'.\nSee 
`run-hooks'." :type (quote hook) :group (quote vc)))
|   eval-defun-2()
|   eval-defun(nil)
|   call-interactively(eval-defun nil nil)
`----

It looks to me that it is an issue of orphaned "comma".

4. I am attaching a fix.

Hopefully it is OK.

ps: My next commit will come with all the ceremony.  Until then ...
-- 

=== modified file 'lisp/custom.el'
--- lisp/custom.el      2012-06-27 07:10:27 +0000
+++ lisp/custom.el      2012-08-07 19:45:37 +0000
@@ -337,7 +337,7 @@
          ;; expression is checked by the byte-compiler, and that
          ;; lexical-binding is obeyed, so quote the expression with
          ;; `lambda' rather than with `quote'.
-         ``(funcall #',(lambda () ,standard))
+        `(list 'funcall (lambda () ,standard))
        `',standard)
     ,doc
     ,@args))