Add *,**,@ to index, as suggested by
http://farmdev.com/thoughts/24/what-does-the-def-star-variable-or-def-asterisk-parameter-syntax-do-in-python-/

The right entry type to use isn't clear; operator seems wrong, because *,**,@
aren't being used in expressions here.  I put them as 'statement'; 'syntax'
might be better.
diff --git a/Doc/tutorial/controlflow.rst b/Doc/tutorial/controlflow.rst
index 420c8d9..61a621f 100644
--- a/Doc/tutorial/controlflow.rst
+++ b/Doc/tutorial/controlflow.rst
@@ -437,6 +437,9 @@
 Arbitrary Argument Lists
 ------------------------
 
+.. index::
+  statement: *  
+
 Finally, the least frequently used option is to specify that a function can be
 called with an arbitrary number of arguments.  These arguments will be wrapped
 up in a tuple.  Before the variable number of arguments, zero or more normal
@@ -464,6 +467,9 @@
    >>> range(*args)            # call with arguments unpacked from a list
    [3, 4, 5]
 
+.. index::
+  statement: **
+
 In the same fashion, dictionaries can deliver keyword arguments with the ``**``\
 -operator::