Copysign
Returns the absolute value of the first parameter, with the sign of the second parameter.
_Decimal64 __d64_copysign (_Decimal64, _Decimal64); _Decimal128 __d128_copysign (_Decimal128, _Decimal128);
_Decimal64 __d64_copysign (_Decimal64, _Decimal64);
_Decimal128 __d128_copysign (_Decimal128, _Decimal128);