Add more aliases to synchronize IPv4 and IPv6 tunnel command, e.g.,
  IPv4: hoplimit (alias to ttl), tclass (alias to tos)
  IPv6: dsfield, tos (alias to tc, or tclass), ttl (alias to hoplimit)
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Stephen Hemminger <stephen.hemminger@vyatta.com>