Add changelog for Qt 5.7.0 release

Change-Id: Ic683b32daa35fc771f848046b26fd6edfdaaa0c7
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>

dist/changes-5.7.0

@@ -0,0 +1,39 @@
+Qt 5.7 introduces new features and improvements as well as bugfixes
+over the 5.6.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://doc.qt.io/qt-5/index.html
+
+The Qt version 5.7 series is binary compatible with the 5.6.x series.
+Applications compiled for 5.6 will continue to run with 5.7.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  https://bugreports.qt.io/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                           Library                                        *
+****************************************************************************
+
+QtBluetooth
+-----------
+
+ - Added API for Bluetooth Low Energy Peripheral support. This new API is
+   a Technology Preview and currently only supported on BlueZ.
+ - [QTBUG-52428] Added QLowEnergyConnectionParameters class to enable
+   adjustment of BTLE connection parameters
+ - Added operator!= for QBluetoothUuid
+ - Added Bluetooth Low Energy signed write support on Linux/BlueZ and Android
+
+****************************************************************************
+*                      Platform Specific Changes                           *
+****************************************************************************
+
+iOS/tvOS
+--------
+
+ - Added support for QtBluetooth on tvOS.