af-packet: declare TP_STATUS_VLAN_VALID if needed

Some old distribution don't ship recent enough linux header. This
result in TP_STATUS_VLAN_VALID being undefined. This patch defines
the constant and use it as it is used in backward compatible method
in the code: the flag is not set by kernel and a test on vci value
will be made.

This should fix https://redmine.openinfosecfoundation.org/issues/1106

PR builds:
- PR build: https://buildbot.suricata-ids.org/builders/regit/builds/108
- PR pcaps: https://buildbot.suricata-ids.org/builders/regit-pcap/builds/47