Fix: wrong sasize in sockgetchar/sockrecvfrom

On receive, the struct sockaddr is zeroed and does not have an address
family until recvfrom fills it in.  SASIZE assumes that if there is no
address family, it is INET.  This means that for IPv6 UDP sockets, the
sockaddr is truncated and the reply is forwarded to the wrong address.
Instead, use sizeof(PROXYSOCKADDRTYPE).

src/sockgetchar.c

@@ -63,7 +63,7 @@ int sockrecvfrom(struct clientparam *param, SOCKET sock, struct sockaddr * sin,
 	if(conf.timetoexit) return EOF;
 	res = param?param->srv->so._poll(param->sostate, &fds, 1, to):so._poll(so.state, &fds, 1, to);
 	if (res<1) return 0;
-	sasize = SASIZE(sin);
+	sasize = sizeof(PROXYSOCKADDRTYPE);
 	do {
 		res = param?param->srv->so._recvfrom(param->sostate, sock, (char *)buf, bufsize, 0, (struct sockaddr *)sin, &sasize):so._recvfrom(so.state, sock, (char *)buf, bufsize, 0, (struct sockaddr *)sin, &sasize);
 	} while (res < 0 && (errno == EAGAIN || errno == EINTR));