Update changelog for 5.2.1

Change-Id: I6e8d2dbf129092c53331c639a767ca4955212f77
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

dist/changes-5.2.1

+Qt 5.2.1 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.2.0.
+
+For more details, refer to the online documentation included in this
+distribution. The documentation is also available online:
+
+  http://qt-project.org/doc/qt-5.2
+
+The Qt version 5.2 series is binary compatible with the 5.1.x series.
+Applications compiled for 5.1 will continue to run with 5.2.
+
+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                                         *
+****************************************************************************
+
+QtQml
+-----
+
+ - [QTBUG-35979] Fixed JavaScript Array.pop() not updating the
+   internal array length correctly
+
+QtQuick
+-------
+
+ - [QTBUG-35128] Fixed TextInput to call fixup() on its validator when
+   being accepted or losing focus, and the validator reports that the input
+   is in "intermediate" state ie. the input should be fixed up.
+ - [QTBUG-34517] Fixed an issue that caused QQuickTextInput to not
+   accept delete/home/backspace/left/right keys when the key was used
+   in a shortcut.