Add changes file for 5.7.1

Change-Id: I04f2b68c41c5a0946707956d2efbc4384797b807
Reviewed-by: Giulio Camuffo <giulio.camuffo@kdab.com>

dist/changes-5.7.1

+Qt 5.7.1 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.7.0.
+
+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.
+
+Qt Wayland General
+-------
+
+- Build no longer fails with QT_NO_ACCESSIBILITY defined
+- Fixed source tarballs not compiling with --developer-build configure flag
+- Namespaced builds no longer failing
+
+Qt Wayland QPA Plugin
+-------
+
+- Fixed window decorations not being removed or added when toggling fullscreen
+- Fixed drag and drop from the application to itself when running on Weston
+- Improved the HIDPI support
+- Fixed a crash when dragging a window with touch input and no pointer
+- Fixed a crash on application exit
+- Made it use the proper activation mechanism when using xdg_shell
+- Fixed returning to the same window size when unmaximizing on xdg shell
+- Fixed the window resize area being too big on the bottom and right edges
+- Support for EGL_KHR_platform_wayland
+
+Qt Compositor API Tech Preview
+-------
+
+- Added a minimal-qml example
+- ShellSurfaceItem now sends unmaximize configure events with zero width and height for xdg_shell
+- Added missing NOTIFY signal for the bufferLocked property
+- Fixed touch release events getting stuck in some cases
+- Fixed wrong key code of key events when control was pressed
+- Popup fixes
+- Drag-and-drop fixes