[NET]: Convert link dumping to new netlink api

Transforms netlink code to dump link tables to use the new
netlink api. Makes rtnl_getlink() available regardless of the
availability of the wireless extensions.

Adding copy_rtnl_link_stats() avoids the structural dependency
of struct rtnl_link_stats on struct net_device_stats and thus
avoids troubles later on.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>