Add cPickle to the list of modules in the chapter.
diff --git a/Doc/lib/libpython.tex b/Doc/lib/libpython.tex
index 2b03e97..944f80f 100644
--- a/Doc/lib/libpython.tex
+++ b/Doc/lib/libpython.tex
@@ -28,6 +28,9 @@
 \item[pickle]
 --- Convert Python objects to streams of bytes and back.
 
+\item[cPickle]
+--- Faster version of \module{pickle}, but not subclassable.
+
 \item[copy_reg]
 --- Register \module{pickle} support functions.