Snabbmark benchmark for RawSocket and Intel10g

[dpino]

This PR adds two new benchmarks in snabbmark. One for RawSocket and another one for Intel10g.

Benchmarking RawSocket on veth interfaces:

$ sudo SNABB_IFNAME0=veth0 SNABB_IFNAME1=veth1 ./snabb snabbmark rawsocket
No PMU available: single core cpu affinity required
Packets: 10000; Packet Size: 64; Timeout: 1000
Sending through veth0 (9e:10:e6:df:5c:68); Receiving through veth1 (d6:13:9f:37:76:1c)

Processed 0.0 million packets in 0.19 seconds (rate: 0.1 Mpps, 0.03 Gbit/s, 0.00 % packet loss).

Benchmarking Intel10g on PCI:

$ sudo SNABB_PCI0=0000:82:00.0 SNABB_PCI1=0000:02:00.0 ./snabb snabbmark intel10g 10e6 550
No PMU available: single core cpu affinity required
Sending through nic0 (82:00.0); Receiving through nic1 (02:00.0)

Processed 10.0 million packets in 4.74 seconds (rate: 2.1 Mpps, 8.65 Gbit/s, 0.04 % packet loss).