Add changelog for 5.3.1

Change-Id: I5b3fb1c9e6b91bcf58b72f6e380c3cd580674f3c
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Merge remote-tracking branch 'origin/5.3.1' into 5.3

Change-Id: I433651eb5ccc66d74fa2dcf508e5fde44e4ed5db