Added 1.6.4 release note stub.

docs/releases/1.6.4.txt

+==========================
+Django 1.6.4 release notes
+==========================
+
+*Under development*
+
+Django 1.6.4 fixes several bugs in 1.6.3.
+
+Bugfixes
+========
+
+* Added backwards compatibility support for the :mod:`django.contrib.messages`
+  cookie format of Django 1.4 and earlier to faciliate upgrading to 1.6 from
+  1.4 (`#22426 <http://code.djangoproject.com/ticket/22426>`_).

docs/releases/index.txt

@@ -36,6 +36,7 @@ Final releases
 .. toctree::
    :maxdepth: 1
 
+   1.6.4
    1.6.3
    1.6.2
    1.6.1