[master] 8943203 Mention UDS effects on VMOD std in "Upgrading to 6.0".

[Geoff Simmons]

commit 89432039dc5eeca8810b6b0de890326026af5cdc
Author: Geoff Simmons <geoff at uplex.de>
Date:   Thu Mar 8 10:34:07 2018 +0100

    Mention UDS effects on VMOD std in "Upgrading to 6.0".

diff --git a/doc/sphinx/whats-new/upgrading-6.0.rst b/doc/sphinx/whats-new/upgrading-6.0.rst
index 8cfcb67..db8c9cd 100644
--- a/doc/sphinx/whats-new/upgrading-6.0.rst
+++ b/doc/sphinx/whats-new/upgrading-6.0.rst
@@ -206,6 +206,14 @@ protocol is not used, then ``0.0.0.0`` will be added to
 Again, this is probably not a concern if ``client.ip`` is set via the
 PROXY protocol.
 
+VMOD std
+--------
+
+The VMOD std function :ref:`func_port` always returns 0 when applied
+to a ``*.ip`` variable whose value is set to ``0.0.0.0`` because the
+listener is UDS.  :ref:`func_set_ip_tos` is silently ignored when the
+listener is UDS.
+
 VCL variables
 ~~~~~~~~~~~~~