Add changes file for Qt 5.9.2

Change-Id: Ied8ae1a13533b637849c2c772b99e78d5309d709
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

dist/changes-5.9.2

+Qt 5.9.2 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.9.0.
+
+For more details, refer to the documentation included in this distribution.
+The documentation is also available online:
+
+https://doc.qt.io/qt-5/
+
+The Qt version 5.9 series is binary compatible with the 5.8.x series.
+Applications compiled for 5.8 will continue to run with 5.9.
+
+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 5.9.2 Changes                           *
+****************************************************************************
+
+  - Added documentation on expressing supported Apple OS version in
+    application projects.
+  - Updated the tutorial for Getting Started on Qt Widgets.
+  - Updated documentation on Qt Platform Abstraction and added a list of
+    QPA plugins.
+  - Updated description of Qt features in Qt Configure Options.
+  - Fixed several instances of missing, incorrect, or obsolete information.