avoid negating LONG_MIN in cash_out()

Hi,
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