Add changelog for 5.6.1

Change-Id: Id905cf856ef026dd5270235eededaa65e6d31b66
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

dist/changes-5.6.1

+Qt 5.6.1 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.6.0.
+
+For more details, refer to the online documentation included in this
+distribution. The documentation is also available online:
+
+  http://doc.qt.io/qt-5.6/
+
+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.
+
+****************************************************************************
+*                         Platform Specific Changes                        *
+****************************************************************************
+Android
+-------
+- [QTBUG-51198] Fixed problem with clipping when High DPI mode is enabled.
+
+iOS
+---
+- The minibrowser example will now load non-https URLs.
+- [QTBUG-48221] Improved the usability together with QQuickWidget.