Three-touchpoint fix for the option level collision (option 4 reads
as TCP_KEEPIDLE at SOL_SOCKET vs IP_TOS at IPPROTO_IP):
1. relibc/src/platform/redox/socket.rs: setsockopt/getsockopt
wire format changed from [SocketCall, option] to
[SocketCall, level, option]. The stale 'TODO convert back to
match when we support more levels' comment removed.
2. base/netstack/src/scheme/socket.rs: SocketT::set_sock_opt and
get_sock_opt now take (level, name) separately. The scheme dispatch
reads metadata[1] as level and metadata[2] as option.
3. base/netstack/src/scheme/{tcp,udp}.rs: TCP and UDP SocketT impls
updated to the new (level, name) signature.
vasilito
0c9758886d