Nflog v5.6

Hi Victor,
this branch version fixes your last comments [https://github.com/inliniac/suricata/pull/964]
I've tested it with prscript, and should not be any problem:

https://buildbot.suricata-ids.org/builders/glongo/builds/1
https://buildbot.suricata-ids.org/builders/glongo-pcap/builds/1