Add a reference to the signal module to the os.kill() description.
This closes SF bug #495609.
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index f09259d..9493c20 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -980,7 +980,9 @@
\begin{funcdesc}{kill}{pid, sig}
\index{process!killing}
\index{process!signalling}
-Kill the process \var{pid} with signal \var{sig}.
+Kill the process \var{pid} with signal \var{sig}. Constants for the
+specific signals available on the host platform are defined in the
+\refmodule{signal} module.
Availability: \UNIX.
\end{funcdesc}