feature #5977 RequestStack parameter is required since 3.0 (leunggamciu)

This PR was submitted for the 3.0 branch but it was merged into the 2.8 branch instead (closes #5977).

Discussion
----------

RequestStack parameter is required since 3.0

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 3.0
| Fixed tickets | N/A

Commits
-------

cb54c5e RequestStack parameter is required since 3.0

components/http_kernel/introduction.rst

@@ -616,6 +616,7 @@ However, the HttpKernel component comes with some built-in listeners and
 a built-in ControllerResolver that can be used to create a working example::
 
     use Symfony\Component\HttpFoundation\Request;
+    use Symfony\Component\HttpFoundation\RequestStack;
     use Symfony\Component\HttpFoundation\Response;
     use Symfony\Component\HttpKernel\HttpKernel;
     use Symfony\Component\EventDispatcher\EventDispatcher;
@@ -641,7 +642,7 @@ a built-in ControllerResolver that can be used to create a working example::
     $matcher = new UrlMatcher($routes, new RequestContext());
 
     $dispatcher = new EventDispatcher();
-    $dispatcher->addSubscriber(new RouterListener($matcher));
+    $dispatcher->addSubscriber(new RouterListener($matcher, new RequestStack()));
 
     $resolver = new ControllerResolver();
     $kernel = new HttpKernel($dispatcher, $resolver);