std::shared_ptr supports it. To resolve an ambiguous overload when a
literal 0 is passed as a parameter, the normal constructors needed to be
made a template, like std::shared_ptr.
Task-number: QTBUG-52569
Change-Id: Id75834dab9ed466e94c7ffff14451417892d2148
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>