[master] 7c9916a Add test which provoked #2184

[Poul-Henning Kamp]

commit 7c9916a6eb046b2cd81b6c7c23e42bc3ddb424a0
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Jan 16 08:35:14 2017 +0000

    Add test which provoked #2184

diff --git a/bin/varnishtest/tests/v00020.vtc b/bin/varnishtest/tests/v00020.vtc
index 42f0f8e..5f36a6c 100644
--- a/bin/varnishtest/tests/v00020.vtc
+++ b/bin/varnishtest/tests/v00020.vtc
@@ -78,6 +78,8 @@ varnish v1 -vcl {
 
 		set req.http.foo = now - now;
 
+		set req.http.foo = 1- -1;
+
 		set req.http.foo = 1 + 1;
 		set req.http.foo = 1 - 1;
 		set req.http.foo = 3 * 2;