New section header style.

Fix up a few synopses.
diff --git a/Doc/lib/libsignal.tex b/Doc/lib/libsignal.tex
index 86d6967..ee68ace 100644
--- a/Doc/lib/libsignal.tex
+++ b/Doc/lib/libsignal.tex
@@ -1,4 +1,5 @@
-\section{Built-in Module \module{signal}}
+\section{\module{signal} ---
+         Set handlers for asynchronous events.}
 \declaremodule{builtin}{signal}