iosource: pcap_set_timeout vs pcap_set_immediate

Hi all,

looking at PcapSource::OpenLive() in iosource/pcap/ I was
wondering whether it would be better to use pcap_set_immediate instead
of "setting the smallest time-out possible" with pcap_set_timeout.

Could it be that, especially in high-throughput environments, the
introduced timeout in polling on the socket buffer may cause initial
packet loss?