Add changes file for 5.6

Change-Id: I938c275371b4287f9da9148732505beaadbae90d
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

dist/changes-5.6.0

@@ -0,0 +1,41 @@
+Qt 5.6 introduces many new features and improvements as well as bugfixes
+over the 5.5.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://doc.qt.io
+
+The Qt version 5.6 series is binary compatible with the 5.5.x series.
+Applications compiled for 5.5 will continue to run with 5.6.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  http://bugreports.qt.io
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                   Important Behavior Changes                             *
+****************************************************************************
+
+- For security reasons, MNG and JPEG 2000 handlers will no longer be
+  built by default, unless the required codec library is found on the
+  system. I.e., the bundled 3rd party libraries will by default not be
+  used. In practice, this means that the qmng and qjp2 handlers will
+  not be present by default.
+
+  The reason is that upstream development of those codes libraries has
+  stalled, so security issues are not addressed.
+
+  Users who still want these handlers using the bundled libraries can
+  easily build them from the source projects:
+  src/plugins/imageformats/jp2/jp2.pro
+  src/plugins/imageformats/mng/mng.pro
+
+****************************************************************************
+*                           General                                        *
+****************************************************************************
+
+- Bundled libwebp updated to version 0.4.4.
+- Bundled libtiff updated to version 4.0.6.