[IPV6]: Fix ipv6 address fetching in raw6_icmp_error().

Fixes kernel bugzilla 10437

Based almost entirely upon a patch by Dmitry Butskoy.

When deciding what raw sockets to deliver the ICMPv6
to, we should use the addresses in the ICMPv6 quoted
IPV6 header, not the top-level one.

Signed-off-by: David S. Miller <davem@davemloft.net>