Bug1082 af packet

Here's the beginning of a fix for bug #1082. It only fixes the issue for af_packet by getting the VLAN id from VLAN header. Kernel stripping VLAN id did appear in Linux 3.0. So I've added a test on Linux version.

I will try to fix PF_RING case in an other request as it seems it is more difficult to get the VLAN info in that case.

Redmine tickets: https://redmine.openinfosecfoundation.org/issues/1082

PR builds:
- PR build: https://buildbot.suricata-ids.org/builders/regit/builds/106
- PR pcaps: https://buildbot.suricata-ids.org/builders/regit-pcap/builds/45