Backported socket library edits + testing tool from LL branch

test/resolve.cpp

@@ -0,0 +1,20 @@
+#include "../lib/socket.cpp"
+#include <iostream>
+#include <sstream>
+#include <string>
+
+int main(int argc, char **argv){
+  if (argc < 2){return 1;}
+  if (argc > 2){
+    std::cout << "Best IPv4 guess:"
+              << Socket::resolveHostToBestExternalAddrGuess(argv[1], AF_INET, argv[2]) << std::endl;
+    std::cout << "Best IPv6 guess:"
+              << Socket::resolveHostToBestExternalAddrGuess(argv[1], AF_INET6, argv[2]) << std::endl;
+  }else{
+    std::cout << "Best IPv4 guess:" << Socket::resolveHostToBestExternalAddrGuess(argv[1], AF_INET)
+              << std::endl;
+    std::cout << "Best IPv6 guess:" << Socket::resolveHostToBestExternalAddrGuess(argv[1], AF_INET6)
+              << std::endl;
+  }
+  return 0;
+}