VPP-1001 - update AF Packet Driver to for modern kernels

VPP-1001 - update AF Packet Driver to for modern kernels

1. Add VNET headers support for checksumming - required
to operate correctly on any recent Linux

2. Bypass QDISC on transmit - improves performance by ~ 5%.
Enabled only if the macro is detected - apparently not
present on archaic distributions.

This still does not solve all issues with TSO - it can be
fixed only by going to tpacket v3 and dynamic rx ring as
well as significant changes in the TX (sendmmsg?).

Change-Id: Iea14ade12586c0a8da49e6dd1012108a08bc85b3
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>