[master] 7e2b6b3 Mention support for sanitizers in Upgrading to 5.2.

[Geoff Simmons]

commit 7e2b6b3968ebc28800b64ee268ff16c48c75bae9
Author: Geoff Simmons <geoff at uplex.de>
Date:   Thu Sep 14 09:24:39 2017 +0200

    Mention support for sanitizers in Upgrading to 5.2.

diff --git a/doc/sphinx/whats-new/upgrading-5.2.rst b/doc/sphinx/whats-new/upgrading-5.2.rst
index 364cc01..b28c328 100644
--- a/doc/sphinx/whats-new/upgrading-5.2.rst
+++ b/doc/sphinx/whats-new/upgrading-5.2.rst
@@ -265,7 +265,12 @@ Other changes
     it possible for VMOD authors to load their code into a debugger
     after a varnishd crash. See :ref:`ref_param_debug`.
 
-  * *XXX: anything else, such as sanitizer flags?*
+  * The project build tools now facilitate the use of sanitizer flags
+    (``-fsanitize`` for the compiler and ``ld``), for undefined
+    behavior, threads, addresses and memory. See the options
+    ``--enable-ubsan``, ``--enable-tsan``, ``--enable-asan`` and
+    ``--enable-msan`` for the ``configure`` script generated by
+    autoconf.
 
   * *XXX: ...*