merged branch Inori/consistent-util-classes (PR #5879)

This PR was squashed before being merged into the master branch (closes #5879).

Commits
-------

07bd5c6 Make non-instantiable utils classes consistent with each other

Discussion
----------

Make non-instantiable utils classes consistent with each other

Bug fix: no
Feature addition: no
Backwards compatibility break: no
Symfony2 tests pass: yes
License of the code: MIT

As per discussion in #5875 turned out that we don't have a consistent way to define non-instantiatable classes.

I don't like `final` as it removes flexibility with no visible gain.
I don't like `abstract` since it's not specifically clear what is meant by that. Is this class not complete? Should it be extended?

src/Symfony/Component/Form/Util/FormUtil.php

@@ -14,7 +14,7 @@ namespace Symfony\Component\Form\Util;
 /**
  * @author Bernhard Schussek <bschussek@gmail.com>
  */
-abstract class FormUtil
+class FormUtil
 {
     /**
      * Map english plural to singular suffixes
@@ -97,6 +97,11 @@ abstract class FormUtil
         array('xuae', 4, false, true, 'eau'),
     );
 
+    /**
+     * This class should not be instantiated
+     */
+    private function __construct() {}
+
     /**
      * Returns the singular form of a word
      *

src/Symfony/Component/Security/Core/Util/ClassUtils.php

@@ -36,6 +36,11 @@ class ClassUtils
      */
     const MARKER_LENGTH = 6;
 
+    /**
+     * This class should not be instantiated
+     */
+    private function __construct() {}
+
     /**
      * Gets the real class name of a class name that could be a proxy.
      *

src/Symfony/Component/Security/Core/Util/StringUtils.php

@@ -16,11 +16,12 @@ namespace Symfony\Component\Security\Core\Util;
  *
  * @author Fabien Potencier <fabien@symfony.com>
  */
-final class StringUtils
+class StringUtils
 {
-    final private function __construct()
-    {
-    }
+    /**
+     * This class should not be instantiated
+     */
+    private function __construct() {}
 
     /**
      * Compares two strings.