struct esi_data is only used with OLD_ESI

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5757 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache.h

@@ -94,7 +94,9 @@ struct objhead;
 struct objcore;
 struct storage;
 struct workreq;
+#ifdef OLD_ESI
 struct esidata;
+#endif
 struct vrt_backend;
 struct cli_proto;
 struct ban;