I extracted the definition of `sockaddr_storage` from each platform when I originally wrote it, and in theory C defines it as "large enough to hold all addresses," so I would rather mirror C as closely as possible in libc.rs rather than making our own enumerations.

I think it's safe to assume that linux at large is the same, it's just the major platforms that we support (freebsd/linux/osx/windows) will probably have differences, but within those distributions I would imagine that a difference is rare.