Add changes-5.1.0 file

Change-Id: I3ade90a360ccece54ac07b1c0c7f71d5bdffc3a4
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>

dist/changes-5.1.0

+Qt 5.1 introduces many new features and improvements as well as bugfixes
+over the 5.0.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-5.1
+
+The Qt version 5.1 series is binary compatible with the 5.0.x series.
+Applications compiled for 5.0 will continue to run with 5.1.
+
+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.
+
+****************************************************************************
+*                           General                                        *
+****************************************************************************
+
+Qt Assistant
+------------
+
+ - [QTBUG-30110] List supported file formats in search indexing.
+
+Qt Designer
+-----------
+
+ - [QTBUG-9502] Rich text editor: Add support for Right-to-Left blocks.
+ - [QTBUG-25872] Fix moving widgets in horizontal layouts in RTL mode.
+ - [QTBUG-26394] Use multiline validation for dynamic string properties.
+ - [QTBUG-29234] ActiveQt plugin: Load control string correctly.
+ - [QTBUG-29234] ActiveQt plugin: Fix setting a control by task menu.
+ - [QTBUG-29904] Aero-Style-QWizard: Remove special handling in Qt Designer.
+
+Qt Linguist
+-----------
+
+ - make linguist tools suitable for cross-building
+ - purge TS 1.1 support from linguist tools
+ - purge CODECFORTR & -codecfortr support from linguist tools
+ - [QTBUG-27238] Make linguist's source viewer read all files as UTF-8.
+
+ - lupdate
+
+   * purge ui3 support from lupdate
+