Fix usage string.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1014 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishtop/varnishtop.c

@@ -38,7 +38,7 @@ static unsigned ntop;
 static void
 usage(void)
 {
-	fprintf(stderr, "usage: varnishtop [-1V]\n");
+	fprintf(stderr, "usage: varnishtop %s [-1V]\n", VSL_USAGE);
 	exit(1);
 }