ColumnReader and sink can cause deadlock on host-side bus

[johanpel]

When a ColumnReader has delivered all elements to the stream, as far as the sink is concerned, the ColumnReader is done doing its job. Thus it might reset the ColumnReader before all bus transfers on the host-side of the bus have been handled by the ColumnReader. This can cause a deadlock on the host side bus as the resetted ColumnReader will not acknowledge any incoming transfers that might still be open from a large burst request.

Solution is probably to provide a "done" signal on the output of the ColumnReader, or to "un-fix" the burst length so we never burst over our last byte of interest.

[johanpel]

Users can use the unlock stream for this.