Update DtoConstFP() to be correct after LLVM r67562, which changed the way the APFloat constructor expects its i80 APInts to be formatted. (They're now actually consistent with the x87 format)

module complex2;

void main()
{
    cdouble c = 3.0 + 0i;
    cdouble d = 2.0 + 0i;
    cdouble c1 = c + 3.0;
    cdouble c2 = c - 3.0i;
    cdouble c3 = c / 2.0;
}