Add changes file for 5.9.1

Change-Id: Ife0ddc6788ddfe64e6e27e5b7403064cddcf636a
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

dist/changes-5.9.1

+Qt 5.9.1 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 online documentation included in this
+distribution. The documentation is also available online:
+
+http://doc.qt.io/qt-5/index.html
+
+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.
+
+****************************************************************************
+*                          Library                                         *
+****************************************************************************
+
+QtMultimedia
+------------
+
+- Fixed overflow in the QML MediaPlayer/Audio items loop counter.
+
+****************************************************************************
+*                      Platform Specific Changes                           *
+****************************************************************************
+
+Android
+-------
+
+- [QTBUG-61085] Fixed crash in OpenSL ES input device caused by over-committing
+  the device with data.
+
+macOS & iOS
+-----------
+
+- [QTBUG-50588] Fixed the StoppedState signal in the media-recorder, so it's not
+  emitted before the file has been written.