enable support for complex @ int

[Gunter]

enable basic operators for mixed types:

• c+i; i+c; i-c; c-i; i*c; c*i; i/c; c/i;

The implementation should be roughly like

template<R> std::complex<R> operator+ (int in1, const std::complex<R>& in2 ){
    return typename std::complex<R>::value_type(in1) + in2;
}

plus a carefully chosen enable_if to avoid "ambigous overload" errors when R is int

[anonymous]

it's an old bug but now this is possible with ublas.