rem: int io_multiplex_write(int f, char *buf, int len)
add: int io_multiplex_write(enum logcode code, char *buf, int len)
context: int io_multiplex_write(int f, char *buf, int len){	if (!io_multiplexing_out) return 0;	io_flush();	SIVAL(io_buffer-4, 0, ((MPLEX_BASE + f)<<24) + len);	memcpy(io_buffer, buf, len);	stats.total_written += (len+4);	writefd_unbuffered(multiplex_out_fd, io_buffer-4, len+4);	return 1;}