This makes implementing class methods that enable or disable a feature
stored in a QFlags<> member easier.
[ChangeLog][QtCore][QFlags] Added setFlag method to set or unset a flag
Task-number: QTBUG-27100
Change-Id: Ic602abbbf3100df78f21b7918573744d1bbd18c1
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>