add versionadded info

Doc/lib/libzipfile.tex

@@ -165,6 +165,8 @@ cat myzip.zip >> python.exe
         by the ZipExtFile, allowing it to operate independently of the 
         ZipFile.
     \end{notice}
+
+    \versionadded{2.6}
 \end{methoddesc}
 
 \begin{methoddesc}{printdir}{}