swift

f1f4ff58 - Fix negation of 0 length Decimal

Fix negation of 0 length Decimal A Decimal value with _length 0 and _isNegative set to 1 is interpreted as a NaN. The 'negate()' function however, flipped the _isNegative flag without regard for the _length 0 case. This meant that -0 would become NaN. The fix checks for the _length 0 special case. In NSDecimalSubtract() the same check was performed. Since this now happens in negate(), it is removed from the NSDecimalSubtract() function.