[master] 32090ef document the legal PROXY protocol versions

[Nils Goroll]

commit 32090ef3da34b1c8f589fb8731e18a7ccadbc319
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Nov 2 18:34:05 2016 +0100

    document the legal PROXY protocol versions

diff --git a/doc/sphinx/reference/vcl.rst b/doc/sphinx/reference/vcl.rst
index d9f10fc..cc2b5bb 100644
--- a/doc/sphinx/reference/vcl.rst
+++ b/doc/sphinx/reference/vcl.rst
@@ -238,7 +238,7 @@ are available:
 
   proxy_header
     The PROXY protocol version Varnish should use when connecting to
-    this backend.
+    this backend. Allowed values are ``1`` and ``2``.
 
   max_connections
     Maximum number of open connections towards this backend. If