Fix#531: Changing signalling of virtual boundary from u(v) to u(13)
As agreed in Goteborg, pps_virtual_boundaries_pos_x[ i ] and pps_virtual_boundaries_pos_y[ i ] are coded as u(13)
As agreed in Goteborg, pps_virtual_boundaries_pos_x[ i ] and pps_virtual_boundaries_pos_y[ i ] are coded as u(13)