[WIP] Add getsockopt and setsockopt and setsockopt syscalls to WASI.

[loganek]

This is a proposal to expose the functionality directly from posix as oposite to having function per option (we already have placeholders for some of that). Exposing get/setsockopt functions gives us more flexibility; we can still limit the parameters by modifying __wasi_sock_opt_so_t enumeration.