rem: int io_multiplex_write(enum logcode code, char *buf, int len)
add: int io_multiplex_write(enum logcode code, char *buf, size_t len)
context: int io_multiplex_write(enum logcode code, char *buf, int len){	if (!io_multiplexing_out) return 0;	io_flush();	stats.total_written += (len+4);	mplex_write(multiplex_out_fd, code, buf, len);	return 1;}