Optimization: Type safe GenericListIterator

[gamedevsam]

typedefs don't yield typesafe code. This essentially means each iterator "node" is a Dynamic object which is slow. I recommend using private class HasNext<T> instead of typedef.

[nadako]

I think we should get rid of GenericListIterator at all and provide strictly typed inlineable iterators for each collection. I'm not sure if I'll find time/motivation to work on that soon, but that's how it should be done it seems.