Change char in struct sockaddr_storage to unsigned

[code.jpe_gmail.com]

Summary

This header file is imported by Golang and converted into a native Golang struct. The char type was therefor converted into int8 which causes issues holding IP address octets. This prevents using MCAST_JOIN_GROUP in Golang on FreeBSD with a setsockopt error since octet 224 will wrap to -32.

Bump FreeBSD version to indicate the struct change.