Skip tests if ldap_set_rebind_proc() is not available

This is already done by ldap_set_rebind_proc_error.phpt, but not by the
other two affected tests.

Closes phpGH-16708.

Author: cmb69

ext/ldap/tests/ldap_set_rebind_proc_basic.phpt

@@ -6,7 +6,10 @@ Patrick Allaert <patrickallaert@php.net>
 --EXTENSIONS--
 ldap
 --SKIPIF--
-<?php require_once('skipifbindfailure.inc'); ?>
+<?php
+if (!function_exists('ldap_set_rebind_proc')) die("skip ldap_set_rebind_proc() not available");
+require_once('skipifbindfailure.inc');
+?>
 --FILE--
 <?php
 require "connect.inc";

ext/ldap/tests/ldap_unbind_variation.phpt

@@ -6,7 +6,10 @@ Patrick Allaert <patrickallaert@php.net>
 --EXTENSIONS--
 ldap
 --SKIPIF--
-<?php require_once('skipifbindfailure.inc'); ?>
+<?php
+if (!function_exists('ldap_set_rebind_proc')) die("skip ldap_set_rebind_proc() not available");
+require_once('skipifbindfailure.inc');
+?>
 --FILE--
 <?php
 require "connect.inc";