Backported upstream patch.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Buildbots are missing lex, which is normally a symlink to flex. This
solution is used elsewhere in the package but missing here.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

PF_RING is a high speed packet capture library that turns a commodity PC into an efficient and cheap
network measurement box suitable for both packet and active traffic analysis and manipulation.
Moreover, PF_RING opens totally new markets as it enables the creation of efficient application such as
traffic balancers or packet filters in a matter of lines of codes.

github : https://github.com/ntop/pf_ring
official : https://www.ntop.org

Signed-off-by: BangLang Huang <banglang.huang@foxmail.com>
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
[rename kmod-pfring to kmod-pf-ring]