Remove all uses of \sectcode; we can now use logical markup everywhere.
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 605a63c..1dac264 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -1,4 +1,4 @@
-\section{Built-in Module \sectcode{sys}}
+\section{Built-in Module \module{sys}}
 \label{module-sys}
 
 \bimodindex{sys}