MINOR: sample: Add ipv6 to ipv4 and sint to ipv6 casts

The RFC4291 says that when the IPv6 adress have the followin form:
0000::ffff:a.b.c.d, if can be converted to an IPv4 adress. This patch
enable this conversion in casts.

As the sint can be casted as ipv4, and ipv4 can be casted as ipv6, we
can directly cast sint as ipv6 using the RFC4291.
1 file changed