Some fixes for vc-ignore (Bug#15754).

Inspired by Andreas Politz and Dmitry Gutov.

diff --cc lisp/ChangeLog
index a994cf2,45c2154..18f0a9f
--- 1/lisp/ChangeLog
--- 2/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@@ -1,9 -1,3 +1,14 @@@
++2013-12-25  Xue Fuqiao  <xfq.free@gmail.com>
++
++      * vc/vc.el (vc-ignore): Use `vc-responsible-backend'.
++      Fix interactive spec.  Doc fix.  (Bug#15754)
++
 +2013-12-25  Katsumi Yamaoka  <yamaoka@jpl.org>
 +
 +      * emacs-lisp/byte-run.el (eval-when-compile):
 +      * progmodes/cc-defs.el (cc-eval-when-compile):
 +      Fix edebug spec (bug#16184).
 +
  2013-12-25  Lars Ingebrigtsen  <larsi@gnus.org>
  
        * net/shr.el (shr-visit-file): Remove debugging function.