[5.2] 8ec02a5 Add necessary #include

[PÃ¥l Hermunn Johansen]

commit 8ec02a5d675b106967305228a98ce9f640c3aa7e
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Thu Sep 7 11:16:23 2017 +0000

    Add necessary #include

diff --git a/bin/varnishd/mgt/mgt_shmem.c b/bin/varnishd/mgt/mgt_shmem.c
index d5d5193..2b9741e 100644
--- a/bin/varnishd/mgt/mgt_shmem.c
+++ b/bin/varnishd/mgt/mgt_shmem.c
@@ -34,6 +34,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>