TUNNEL: IPv6-over-IPv6 tunnel support.

TUNNEL: IPv6-over-IPv6 tunnel support.

Fix ip6tunnel.c to be fit with current ip command style.
Unlike other modules currently iptunnel (and ip6tunnel) is not
designed as protocol-independent because of unarranged structure
between IPv4 and IPv6.

Usage: ip -f inet6 tunnel { add | change | del | show } [ NAME ]
          [ remote ADDR local ADDR ] [ dev PHYS_DEV ]
          [ encaplimit ELIM ]
          [ hoplimit HLIM ] [ tc TC ] [ fl FL ]
          [ dscp inherit ]

Where: NAME := STRING
       ADDR := IPV6_ADDRESS
       ELIM := { none | 0..255 }(default=4)
       HLIM := 0..255 (default=64)
       TC   := { 0x0..0xff | inherit }
       FL   := { 0x0..0xfffff | inherit }

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>