update phpunit tests to use different parent class

tests/GeneratePasswordTest.php

@@ -2,7 +2,7 @@
 
 require_once('common.php');
 
-class GeneratePasswordTest extends PHPUnit_Framework_TestCase {
+class GeneratePasswordTest extends \PHPUnit\Framework\TestCase {
     public function testBasic() {
         $one = generate_password();
 

tests/PacryptTest.php

@@ -2,7 +2,7 @@
 
 require_once('common.php');
 
-class PaCryptTest extends PHPUnit_Framework_TestCase {
+class PaCryptTest extends \PHPUnit\Framework\TestCase {
     public function testMd5Crypt() {
         $hash = _pacrypt_md5crypt('test', '');
 

tests/RemoteTest.php

@@ -2,7 +2,7 @@
 
 require_once('common.php');
 
-abstract class RemoteTest extends PHPUnit_Framework_TestCase {
+abstract class RemoteTest extends \PHPUnit\Framework\TestCase {
     protected $server_url = 'http://change.me/to/work'; // http://orange/david/postfixadmin/xmlrpc.php';
     protected $username = 'user@example.com';
     protected $password = 'password1';

tests/ValidatePasswordTest.php

@@ -2,7 +2,7 @@
 
 require_once('common.php');
 
-class ValidatePasswordTest extends PHPUnit_Framework_TestCase {
+class ValidatePasswordTest extends \PHPUnit\Framework\TestCase {
     public function testBasic() {
         $config = Config::getInstance();