Fixed bug on ios due to using texture unit > 8
Fixed bug on ios due to using texture unit > 8

hishamabdelrahman/osgjs,jtorresfabra/osgjs,hishamabdelrahman/osgjs,jtorresfabra/osgjs,cedricpinson/osgjs,hishamabdelrahman/osgjs,jtorresfabra/osgjs,cedricpinson/osgjs,cedricpinson/osgjs