Add changes-5.1.1 file

Change-Id: I1052732f56c234f6c57fa74f4a2ba8cd46ae8081
Reviewed-by: David Faure (KDE) <faure@kde.org>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: Ic32f2f1327095555b9694fffe960af4e27f5ce21