[5.2] fe006c9 Add necessary include

[PÃ¥l Hermunn Johansen]

commit fe006c9ef1b9a4ff58d9845fa1e64769b6dbb4ed
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Thu Sep 7 10:58:14 2017 +0000

    Add necessary include

diff --git a/bin/varnishd/common/common_vsc.c b/bin/varnishd/common/common_vsc.c
index eb40edf..bc8dabf 100644
--- a/bin/varnishd/common/common_vsc.c
+++ b/bin/varnishd/common/common_vsc.c
@@ -30,6 +30,7 @@
 #include "config.h"
 
 #include <errno.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>