Idea: "Frozen" inner function

[Frank Benoit (keinfarbton)]

> My idea was inspired by this. As D has nothing like final, I thought a 
> copy of the outer variables would do as well.

I am not completely sure, but I think this is the way java implements
this. If you imagine that the method can be called multiple times and
the instantiated object can work with different final values, it seams
the values are copied into the object instance.