fix implicit declaration compilation warning

--- src/htmltcl.c.orig	Sun Dec 12 10:19:53 2010
+++ src/htmltcl.c	Sun Dec 12 10:20:10 2010
@@ -41,6 +41,7 @@ static char const rcsid[] = "@(#) $Id: htmltcl.c,v 1.1
 #include <assert.h>
 #include "html.h"
 #include "swproc.h"
+#include "restrack.h"
 
 #include <time.h>