[SAOC 25] improve importC weekly update 13

[Emmanuel]

Hi all,

This week, I fixed complex compile time error when used in tenary 
operators.


```

void foo() {
     double *a;
     double _Complex *b;
     double _Complex zden;
     double c, d;
     zden = c > d? b[0]: a[0];
}
```

in a tenary operator setup like this, DMD reported incompatible 
types between the `double` nd the `double _Complex`. no common 
type handler did not exist for complex types which expected for 
the `double` to be type casted to `double _Complex`.

But then this fix led to more investigations as importC uses 
complex library struct instead of the deprecated fundamental D 
complex type.  And I am still investigating other issues with 
complex numbers to see if I will need to do that transition to 
make C use fundamental complex.