Add additional links and index entries for "argument" and "parameter".

This adds to the work done for issue #15990 (i.e. f44b8d69e5fc and the
commits referenced there).
diff --git a/Doc/faq/programming.rst b/Doc/faq/programming.rst
index 8e218c0..edee68a 100644
--- a/Doc/faq/programming.rst
+++ b/Doc/faq/programming.rst
@@ -469,6 +469,10 @@
        apply(g, (x,)+args, kwargs)
 
 
+.. index::
+   single: argument; difference from parameter
+   single: parameter; difference from argument
+
 .. _faq-argument-vs-parameter:
 
 What is the difference between arguments and parameters?