Fix protocol being treated as family in getaddrinfo inputs/outputs

[squeek502]

Follow up to #534 (comment)

The Get all adresses for luvit.io test in test-dns.lua now gives:

    { addr = "206.189.225.172", family = "inet", protocol = "tcp", socktype = "stream" },
    { addr = "206.189.225.172", family = "inet", protocol = "udp", socktype = "dgram" },
    { addr = "206.189.225.172", family = "inet", protocol = "ip", socktype = "raw" },
    { addr = "2604:a880:400:d0::1b9f:2001", family = "inet6", protocol = "tcp", socktype = "stream" },
    { addr = "2604:a880:400:d0::1b9f:2001", family = "inet6", protocol = "udp", socktype = "dgram" },
    { addr = "2604:a880:400:d0::1b9f:2001", family = "inet6", protocol = "ip", socktype = "raw" }

which has the correct protocols.

---

Protocol hinting also works, e.g.

local uv = require('luv')

uv.getaddrinfo("luvit.io", nil, {
  protocol = "udp",
}, function (err, res)
  assert(not err, err)
  for i, addr in ipairs(res) do
    print("["..i.."]:")
    for k,v in pairs(addr) do
      print('',k,v)
    end
  end
end)

uv.run()

will give

[1]:
	addr	206.189.225.172
	family	inet
	socktype	dgram
	protocol	udp
[2]:
	addr	2604:a880:400:d0::1b9f:2001
	family	inet6
	socktype	dgram
	protocol	udp