pfring: get vlan id from header

PF_RING is delivering the packet with VLAN header stripped. This
patch updates the code to get the information from PF_RING extended
header information.

This patch uses the new function SCKernelVersionIsAtLeast to know
that we've got a old kernel that do not strip the VLAN header from
the message before sending it to userspace.

Redmine ticket: https://redmine.openinfosecfoundation.org/issues/1109

PR builds:
- PR build: https://buildbot.suricata-ids.org/builders/regit/builds/115
- PR pcaps: https://buildbot.suricata-ids.org/builders/regit-pcap/builds/54