Add Send/Sync traits on LookupHost struct

src/libstd/sys/common/net.rs

@@ -110,6 +110,9 @@ fn next(&mut self) -> Option<io::Result<SocketAddr>> {
     }
 }
 
+unsafe impl Sync for LookupHost {}
+unsafe impl Send for LookupHost {}
+
 impl Drop for LookupHost {
     fn drop(&mut self) {
         unsafe { freeaddrinfo(self.original) }