Genie:  Register sockets syscalls in a namespace

We need a namespace because we can't declare e.g. "using relix::foo;" in
the global namespace.
Genie -> relix:  Move bind() system call
Genie -> relix:  Move listen() system call
Genie -> relix:  Move accept() system call
Genie -> relix:  Move connect() system call
Genie -> relix:  Move shutdown() system call
Genie -> relix:  Move get_sockaddr_name() utility
Genie -> relix:  Move getsockname() system call
Genie -> relix:  Move getpeername() system call
Genie:  NewPairedSocket() -> new_paired_socket()

Also, move the declaration to relix.
Genie -> relix:  Move socketpair() system call
Genie:  NewOTSocket() -> relix::new_tcp_socket()
Genie -> relix:  Move socket() system call
Merge branch 'socket-syscalls'