Add versionadded to doc

Doc/lib/libwsgiref.tex

@@ -5,6 +5,8 @@ Implementation}
 \sectionauthor{Phillip J. Eby}{pje@telecommunity.com}
 \modulesynopsis{WSGI Utilities and Reference Implementation}
 
+\versionadded{2.5}
+
 The Web Server Gateway Interface (WSGI) is a standard interface
 between web server software and web applications written in Python.
 Having a standard interface makes it easy to use an application