FreeBSD defines `sin_len` and `sin6_len` inside `sockaddr_in` and
`sockaddr_in6`. `sockaddr`s come from `getsockname` and `uv_ip4_addr`
will differ in the first byte if libuv doesn't set `sin_len` correctly.
PR-URL: https://github.com/libuv/libuv/pull/2492
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <s@saghul.net>