New section header style.

Fix up a few synopses.
diff --git a/Doc/lib/libposix.tex b/Doc/lib/libposix.tex
index dbfc692..e3f2929 100644
--- a/Doc/lib/libposix.tex
+++ b/Doc/lib/libposix.tex
@@ -1,4 +1,5 @@
-\section{Built-in Module \module{posix}}
+\section{\module{posix} ---
+         The most common \POSIX{} system calls.}
 \declaremodule{builtin}{posix}
 
 \modulesynopsis{The most common \POSIX{} system calls (normally used via module