Make QtSensors use Q_DECL_OVERRIDE

This patch aims to make QtSensors uses Q_DECL_OVERRIDE uniformly across
the module

Task-number: QTBUG-27392
Change-Id: I5f814f93307159175f92e29a9990587c03cce96f
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Bump MODULE_VERSION to 5.2.1

Change-Id: I5082d09607f08c4daad72a8530f7f76feac397fa
Reviewed-by: Matti Paaso <matti.paaso@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I11d540f43baa69f9e857dd793666c1008b217956
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I61deffeb7b61a4157b9ecb77de35f08d47c4e9bd
Fix code snippet in Qt Sensors QML Types documentation.

Change-Id: I5639fb872b8e41cc5c5b5968cf1ddf7e247961e2
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>