[PATCH 2/4] eppic/vhost_net_buffers: Introduce changes for kernel 3.19

Linux kernel commit 56b174256b69 ("net: add rbnode to struct sk_buff"),
moves sk_buff->next into an union of sk_buff->{next/prev/tstamp/rb_node}.
Introduce this structure member change, while traversing the socket
buffer list.

These changes are not compatible with previous kernel versions,
so add vhost_net_buffers script file for kernel version >= 3.19 to
kernel version <= 4.8.

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Atsushi Kumagai <ats-kumagai@wm.jp.nec.com>