[HttpFoundation] fixed a small bug on Windows

src/Symfony/Component/HttpFoundation/ApacheRequest.php

@@ -35,7 +35,7 @@ class ApacheRequest extends Request
 
         if (false === strpos($this->server->get('REQUEST_URI'), $baseUrl)) {
             // assume mod_rewrite
-            return rtrim(dirname($baseUrl), '/');
+            return rtrim(dirname($baseUrl), '/\\');
         }
 
         return $baseUrl;