Revert "deleted abstract method doDisplay (maintain BC)"

This reverts commit 70d90bedce.

lib/Twig/Template.php

@@ -194,6 +194,14 @@ abstract class Twig_Template implements Twig_TemplateInterface
         return ob_get_clean();
     }
 
+    /**
+     * Auto-generated method to display the template with the given context.
+     *
+     * @param array $context An array of parameters to pass to the template
+     * @param array $blocks  An array of blocks to pass to the template
+     */
+    abstract protected function doDisplay(array $context, array $blocks = array());
+
     /**
      * Returns a variable from the context.
      *