avoid negating LONG_MIN in cash_out()

In cash_out(), we have the following code:

    if (value < 0)
    {

        /* make the amount positive for digit-reconstruction loop */
        value = -value;

The negation cannot be represented in type long when the value is LONG_MIN.

It seems we can error out when LONG_MIN is detected instead of continuing with computation.

Please take a look at the patch and provide your feedback.

Thanks