Add sets to list of picklable objects.
diff --git a/Doc/lib/libpickle.tex b/Doc/lib/libpickle.tex
index ef8cb23..ee19ce4 100644
--- a/Doc/lib/libpickle.tex
+++ b/Doc/lib/libpickle.tex
@@ -378,7 +378,7 @@
 
 \item normal and Unicode strings
 
-\item tuples, lists, and dictionaries containing only picklable objects
+\item tuples, lists, sets, and dictionaries containing only picklable objects
 
 \item functions defined at the top level of a module