Add changelog for Qt 5.4.0 release

Change-Id: I4828f4d3d66dd4f6739388d10e91395ed951f3b5
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>

dist/changes-5.4.0

+Qt 5.4 introduces many new features and improvements as well as bugfixes
+over the 5.3.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://qt-project.org/doc/qt-5.4
+
+The Qt version 5.4 series is binary compatible with the 5.3.x series.
+Applications compiled for 5.3 will continue to run with 5.4.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  http://bugreports.qt-project.org/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                          Library                                         *
+****************************************************************************
+
+QtPositioning
+-------------
+
+ - Position:
+   * [QTBUG-39547] Added magneticVariation and magneticVariationValid
+     property to the QML Position type.
+
+ - General:
+   * Weatherinfo end Flickr example improved.
+
+ - QGeoCircle:
+   * [QTBUG-41447] Fixed contains() when rounding errors occur
+
+ - QGeoCoordinate:
+   * [QTBUG-41739] Fixed toString() output in cases when rounding
+     of longitude/latitude is necessary.
+
+****************************************************************************
+*                      Platform Specific Changes                           *
+****************************************************************************
+
+Android
+-------
+
+ - [QTBUG-41873] Fixed wrong initialization of QGeoPositionInfoSource::error()
+   after class instantiation.
+
+iOS
+---
+
+ - [QTBUG-41827] Fixed position retrieval on iOS 8. This was required due
+   to the new authorization scheme in CLLocationManager.
+