SOC_U: Implemented some socket functions

This allows ftpony and ftbrony to work.
It's using Berkeley sockets directly since that's what the soc:U service exposes to applications.
Not sure if there is any chance for alignment issues here. Is there a guarantee that padding won't happen to sizes greater than the types used? (iow is there a guarantee that there won't be inserted any padding between sa_family and sa_data, or any of the other fields in this structure?)

If there's no such guarantee, you'll probably want to use the appropriate packing `#pragma`s.