Fix the synopsis.

Change one \code{} to \samp{}.

Doc/lib/libthreading.tex

 \section{Standard Module \module{threading}}
 \declaremodule{standard}{threading}
 
-\modulesynopsis{None}
+\modulesynopsis{Higher-level threading interfaces.}
 
 
-This module constructs higher-level threading interfaces on top of the
-lower level
-\module{thread} module.
+This module constructs higher-level threading interfaces on top of the 
+lower level \module{thread} module.
 
-This module is safe for use with \code{from threading import *}.  It
+This module is safe for use with \samp{from threading import *}.  It
 defines the following functions and objects:
 
 \begin{funcdesc}{activeCount}{}