[master] 9c7e864 Write up changes concerning restarts in "Upgrading to 6.0".

[Geoff Simmons]

commit 9c7e86416ad6c68140651433c7cd626e8bc61f38
Author: Geoff Simmons <geoff at uplex.de>
Date:   Wed Mar 14 21:03:26 2018 +0100

    Write up changes concerning restarts 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 baff80d..fce4ded 100644
--- a/doc/sphinx/whats-new/upgrading-6.0.rst
+++ b/doc/sphinx/whats-new/upgrading-6.0.rst
@@ -450,6 +450,15 @@ VMOD std
 listener is UDS.  :ref:`std.set_ip_tos(INT) <func_set_ip_tos>` is
 silently ignored when the listener is UDS.
 
+Restarts
+~~~~~~~~
+
+Restarts now leave all of the properties of the client request
+unchanged (all of the ``req.*`` variables, including the headers),
+except for ``req.restarts`` and ``req.xid``, which change by design.
+
+``return(restart)`` can now be called from ``vcl_recv{}``.
+
 New VMODs
 ~~~~~~~~~