Add a version annotation for the help() function.

Doc/lib/libfuncs.tex

@@ -425,6 +425,7 @@ def my_import(name):
   function, class, method, keyword, or documentation topic, and a
   help page is printed on the console.  If the argument is any other
   kind of object, a help page on the object is generated.
+  \versionadded{2.2}
 \end{funcdesc}
 
 \begin{funcdesc}{hex}{x}