Add Socket::Address.from without addrlen

[mamantoha]

I'm not sure why this was implemented this way. The addlen parameter is not necessary when creating an address from a LibC::Sockaddr pointer, as it can be obtained directly within the method.

[straight-shoota]

addrlen is used by the system API for generalization purposes. And yeah it's completely unnecessary for structs with fixed sizes.
So I think we could probably update the entire Address API to deprecate the addrlen parameters. Needs further investigation though.

Looking a bit into this I noticed some weird and unsafe behaviour. We're passing around stack pointers for LibC::SockAddr` outside of their scope. This needs a bit more inspection as well.

Considering this, I'd like to hold this PR for a while until we can look a bit better at the details of what else we want to change.

[ysbaddaden]

We're passing around stack pointers for LibC::SockAddr` outside of their scope.

We never capture the pointer, though.

[straight-shoota]

I think I had seen somewhere a method which returned a pointer to a stack-allocated LibC::Sockaddr*. But I can't find it anymore, so I probably got confused (the socket address code is quite confusing sometimes).