curl: `Curl_socketpair()` fallback vulnerable to man-in-the-middle attack

In Curlsocketpair in curl/lib/socketpair.c if the operating system lacks a native socketpair function, libcurl will create its own pair of sockets. To do this, libcurl first creates a listening socket, then it creates a client socket, which it then connects to the listening socket. During the tim...