cmake DEAL_II_HAVE_COMPLEX_OPERATOR_OVERLOADS examples

dealii/dealii cmake/checks/check_01_cxx_features.cmake :488 

CHECK_CXX_SOURCE_COMPILES(
  "
  #include <complex>

  int main()
  {
    double() * std::complex<float>();
    std::complex<float>() * double();
    float() * std::complex<double>();
    std::complex<double>() * float();
    std::complex<double>() * std::complex<float>();
    std::complex<float>() * std::complex<double>();

    return 0;
  }
  "
  DEAL_II_HAVE_COMPLEX_OPERATOR_OVERLOADS)