Add Myricom SNF API support as a new pcap device.

Add Myricom SNF API support as a new pcap device.

This patch adds support for our NICs when run in a specialized capture mode.
It is diffed against the current master.

The Myricom Sniffer10G software uses Myri-10G programmable Network Interface
Cards (NICs), a firmware extension, a specialized driver and a user-level
library (libsnf) to enable sustained capture of 10-Gigabit Ethernet traffic.
Small-packet coalescing and an efficient zero-copy path to host memory allow
Sniffer10G to capture streams at line rate for all Ethernet packet sizes.

Optionally, libpcap can be used concurrently by multiple processes on a single
NIC port to partition the incoming traffic across processes.  While the Linux
kernel enables this through multiple receive queues, the difference is that the
myri_snf driver cooperates with libsnf to set up multiple queues that are each
independently accessible through user-space.

More information here: http://www.myri.com/scs/SNF/doc

Signed-off-by: Guy Harris <[email protected]>