Skip rcube_ldap_generic test if Net_LDAP3 is not available

tests/Framework/LdapGeneric.php

@@ -13,6 +13,11 @@ class Framework_LdapGeneric extends PHPUnit_Framework_TestCase
      */
     function test_class()
     {
+        // skip test if Net_LDAP3 does not exist
+        if (!class_exists('Net_LDAP3')) {
+            $this->markTestSkipped('The Net_LDAP3 package not available.');
+        }
+
         $object = new rcube_ldap_generic(array());
 
         $this->assertInstanceOf('rcube_ldap_generic', $object, "Class constructor");