make MarbleGraphicsItemPrivate::positions() purely virtual
make MarbleGraphicsItemPrivate::positions() purely virtual

probonopd/marble,rku/marble,quannt24/marble,Earthwings/marble,adraghici/marble,adraghici/marble,quannt24/marble,probonopd/marble,Earthwings/marble,utkuaydin/marble,quannt24/marble,quannt24/marble,tzapzoor/marble,David-Gil/marble-dev,adraghici/marble,probonopd/marble,David-Gil/marble-dev,probonopd/marble,Earthwings/marble,quannt24/marble,rku/marble,Earthwings/marble,quannt24/marble,David-Gil/marble-dev,AndreiDuma/marble,David-Gil/marble-dev,tucnak/marble,quannt24/marble,oberluz/marble,AndreiDuma/marble,oberluz/marble,AndreiDuma/marble,adraghici/marble,utkuaydin/marble,tzapzoor/marble,utkuaydin/marble,tzapzoor/marble,rku/marble,oberluz/marble,Earthwings/marble,utkuaydin/marble,probonopd/marble,utkuaydin/marble,oberluz/marble,tucnak/marble,probonopd/marble,tzapzoor/marble,tzapzoor/marble,tucnak/marble,tucnak/marble,Earthwings/marble,oberluz/marble,David-Gil/marble-dev,adraghici/marble,utkuaydin/marble,rku/marble,tzapzoor/marble,oberluz/marble,tzapzoor/marble,rku/marble,tucnak/marble,tucnak/marble,tucnak/marble,AndreiDuma/marble,AndreiDuma/marble,rku/marble,David-Gil/marble-dev,adraghici/marble,probonopd/marble,tzapzoor/marble,AndreiDuma/marble