SIT or GRE tunnels might want to translate an IPV4 address
into a v4mapped one when translating ICMP to ICMPv6.

This patch adds the parameter to icmp6_send() but
does not change icmpv6_send() signature.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>