vxlan: virtual extensible lan

This is an implementation of Virtual eXtensible Local Area Network
as described in draft RFC:
  http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-02

The driver integrates a Virtual Tunnel Endpoint (VTEP) functionality
that learns MAC to IP address mapping.

This implementation has not been tested only against the Linux
userspace implementation using TAP, not against other vendor's
equipment.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>