Report error from socket read on timeout

A timeout is not considered a transient error (at the socket layer),
and should return -1 rather than 0.

ext/standard/tests/file/fread_socket_variation1.phpt

@@ -20,4 +20,4 @@ fclose($server);
 
 ?>
 --EXPECT--
-string(0) ""
+bool(false)

main/streams/xp_socket.c

@@ -163,7 +163,7 @@ static ssize_t php_sockop_read(php_stream *stream, char *buf, size_t count)
 	if (sock->is_blocked) {
 		php_sock_stream_wait_for_data(stream, sock);
 		if (sock->timeout_event)
-			return 0;
+			return -1;
 	}
 
 	nr_bytes = recv(sock->socket, buf, XP_SOCK_BUF_SIZE(count), (sock->is_blocked && sock->timeout.tv_sec != -1) ? MSG_DONTWAIT : 0);