bug #4856 [Components][Debug] fix DebugClassLoader namespace (xabbuh)

This PR was merged into the 2.5 branch.

Discussion
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[Components][Debug] fix DebugClassLoader namespace

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.5+
| Fixed tickets |

The class loader is located in the Debug component and not in the
ClassLoader component.

Commits
-------

32a589b [Components][Debug] fix DebugClassLoader namespace

components/debug/class_loader.rst

@@ -17,6 +17,6 @@ with a ``DebugClassLoader`` wrapper.
 Using the ``DebugClassLoader`` is as easy as calling its static
 :method:`Symfony\\Component\\Debug\\DebugClassLoader::enable` method::
 
-    use Symfony\Component\ClassLoader\DebugClassLoader;
+    use Symfony\Component\Debug\DebugClassLoader;
 
     DebugClassLoader::enable();