af-packet: leave reading loop at each turn

The idea of this patch is to be sure to leave the ring reading loop
enough to be able to sync counters. This should fix #706.
pcap-file: treat the case of unsupported pcap link

In unix socket mode, Suricata was stopping processing pcap files
when a pcap file with an unsupported datalink was treated. This
patch updates error handling to allow Suricata to treat other
pcap files.
temporarily patched smb + dcerpc parsers for direction demaraction.