IO#ioflush

static VALUE
console_ioflush(VALUE io)
{
#if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
    int fd1 = GetReadFD(io);
    int fd2 = GetWriteFD(io);

    if (fd2 != -1 && fd1 != fd2) {
        if (tcflush(fd1, TCIFLUSH)) sys_fail(io);
        if (tcflush(fd2, TCOFLUSH)) sys_fail(io);
    }
    else {
        if (tcflush(fd1, TCIOFLUSH)) sys_fail(io);
    }
#endif

    return io;
}