[Components][ClassLoader] remove DebugClassLoader

The `DebugClassLoader` has been moved to the Debug component with
Symfony 2.4 and will be removed in 3.0 (see symfony/symfony#13203).

Author: xabbuh

components/class_loader/class_loader.rst

@@ -12,8 +12,7 @@ load all of your project's classes.
 
     You can use both the ``ApcClassLoader`` and the ``XcacheClassLoader`` to
     :doc:`cache </components/class_loader/cache_class_loader>` a ``ClassLoader``
-    instance or the ``DebugClassLoader`` to :doc:`debug </components/class_loader/debug_class_loader>`
-    it.
+    instance.
 
 Usage
 -----

components/class_loader/debug_class_loader.rst

@@ -9,5 +9,4 @@ ClassLoader
     psr4_class_loader
     map_class_loader
     cache_class_loader
-    debug_class_loader
     class_map_generator

components/class_loader/index.rst

@@ -7,7 +7,6 @@
   * :doc:`/components/class_loader/psr4_class_loader`
   * :doc:`/components/class_loader/map_class_loader`
   * :doc:`/components/class_loader/cache_class_loader`
-  * :doc:`/components/class_loader/debug_class_loader`
   * :doc:`/components/class_loader/class_map_generator`
 
 * :doc:`/components/config/index`