Fix dump.name for Windows file paths

Wrong variables were used in line 118 ($file -> $name)

src/Symfony/Component/HttpKernel/DataCollector/DumpDataCollector.php

@@ -115,7 +115,7 @@ public function dump(Data $data)
 
         if (false === $name) {
             $name = strtr($file, '\\', '/');
-            $name = substr($file, strrpos($file, '/') + 1);
+            $name = substr($name, strrpos($name, '/') + 1);
         }
 
         $this->data[] = compact('data', 'name', 'file', 'line', 'fileExcerpt');