[master] 9a9bdf8 Mention the return of umem in "Upgrading to 6.0".

[Geoff Simmons]

commit 9a9bdf8d84e43245d8b32929a70a240930e1bdd2
Author: Geoff Simmons <geoff at uplex.de>
Date:   Wed Mar 14 23:39:48 2018 +0100

    Mention the return of umem 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 c1bef35..2bb277d 100644
--- a/doc/sphinx/whats-new/upgrading-6.0.rst
+++ b/doc/sphinx/whats-new/upgrading-6.0.rst
@@ -661,6 +661,12 @@ of what you will be able to do once VIP 20 is completed.
 Other changes
 =============
 
+* ``varnishd(1)``:
+
+  * The ``umem`` storage allocator, which was removed as of Varnish
+    5.1, has been restored and is now the default on a system where
+    ``libumem`` is available (SunOS and descendants).
+
 * ``varnishlog(1)``:
 
   * Added a third field to the ``ReqStart`` log record that contains the