add versionadded notes

Author: dbu

cookbook/console/generating_urls.rst

@@ -19,6 +19,14 @@ and per Command.
 Configuring the Request Context globally
 ----------------------------------------
 
+.. versionadded: 2.1
+
+    The host and scheme parameters are available since Symfony 2.1
+
+.. versionadded: 2.2
+
+    The base_url parameter is available since Symfony 2.2
+
 To configure the Request Context - which is used by the URL Generator - you can
 redefine the parameters it uses as default values to change the default host
 (localhost) and scheme (http). Starting with Symfony 2.2 you can also configure