Add a sample line for groupdn (commented by default).

ok jmatthew@

src/etc/ypldap.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: ypldap.conf,v 1.3 2012/03/02 07:13:49 ajacoutot Exp $
+# $OpenBSD: ypldap.conf,v 1.4 2012/04/30 12:16:43 ajacoutot Exp $
 
 domain		"example.com"
 interval	60
@@ -13,6 +13,8 @@ directory "127.0.0.1" {
 	binddn "cn=admin,dc=example,dc=com"
 	bindcred "secret"
 	basedn "dc=example,dc=com"
+	# starting point for groups directory search, default to basedn
+	#groupdn "ou=Groups,dc=example,dc=com"
 
 	# passwd maps configuration (RFC 2307 posixAccount object class)
 	passwd filter "(objectClass=posixAccount)"