Make the reference to the os module in the module synopsis (for the

table at the front of the chapter) a hyperlink.

Doc/lib/libposix.tex

@@ -4,7 +4,7 @@
 \declaremodule{builtin}{posix}
   \platform{Unix}
 \modulesynopsis{The most common \POSIX{} system calls (normally used
-                via module \module{os}).}
+                via module \refmodule{os}).}
 
 
 This module provides access to operating system functionality that is