Make internal module references hyperlinks wherever it makes sense.
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index afb4008..1490de4 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -1,7 +1,7 @@
 \section{\module{sys} ---
-         System-specific parameters and functions.}
-\declaremodule{builtin}{sys}
+         System-specific parameters and functions}
 
+\declaremodule{builtin}{sys}
 \modulesynopsis{Access system-specific parameters and functions.}
 
 This module provides access to some variables used or maintained by the
@@ -262,7 +262,7 @@
   a \method{write()} method that takes a string argument.  (Changing these
   objects doesn't affect the standard I/O streams of processes
   executed by \function{os.popen()}, \function{os.system()} or the
-  \function{exec*()} family of functions in the \module{os} module.)
+  \function{exec*()} family of functions in the \refmodule{os} module.)
 \refstmodindex{os}
 \end{datadesc}