Add change file for Qt 5.6.3

Change-Id: I73135f29d5ef8114c8b5b5804144acc8d347299d
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

dist/changes-5.6.3

+Qt 5.6.3 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.6.0.
+
+For more details, refer to the documentation included in this distribution.
+The documentation is also available online:
+
+  https://doc.qt.io/qt-5.6/
+
+The Qt version 5.6 series is binary compatible with the 5.5.x series.
+Applications compiled for 5.5 will continue to run with 5.6.
+
+Some of the changes listed in this file may 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.
+
+****************************************************************************
+*                                 General                                  *
+****************************************************************************
+
+ - Fixed several instances of missing, incorrect or obsolete information.
+ - Updated documentation on supported compilers on Windows 10.