Add tstamp_type/precision support for DAG capture

Add tstamp_precision and tstamp_type support to pcap-dag.c.

Update contact details.

The DAG hardware clock may or may not be synchronsied to either the host clock or an external clock reference, so we can't determine which of PCAP_TSTAMP_ADAPTER or PCAP_TSTAMP_ADAPTER_UNSYNCED is accurate. Either will produce the same result.

The only potential concern is that we don't advertise PCAP_TSTAMP_HOST_* so anyone requesting those explicitly will not be able to capture.