sockets: FD_CLOEXEC

If the user code forks, it inherits open copies of all
lws sockets, which conflict if lws later decides to
close them.

lib/plat/unix/unix-sockets.c

@@ -74,6 +74,8 @@ lws_plat_set_socket_options(struct lws_vhost *vhost, int fd)
 	struct protoent *tcp_proto;
 #endif
 
+	fcntl(fd, F_SETFD, FD_CLOEXEC);
+
 	if (vhost->ka_time) {
 		/* enable keepalive on this socket */
 		optval = 1;