openldap: update copyright dates

Signed-off-by: W. Michael Petullo <mike@flyn.org>

libs/openldap/Makefile

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2006-2012 OpenWrt.org
+# Copyright (C) 2006-2015 OpenWrt.org
 #
 # This is free software, licensed under the GNU General Public License v2.
 # See /LICENSE for more information.