Fix all the dynamic_casts

[haekb]

So I discovered in https://github.com/haekb/nolf2-modernizer/issues/62 there's a technique they use to cast from a base type (or a similar type that has the same base type) up to a more specialized type. This works in Visual C++ 6.0, but not in anything else.

There's a code sample in that ticket that'll show how to reproduce the problem. So now I need to check every single dynamic_cast to make sure it'll work in newer compilers. Ugh.

[haekb]

Ok the extent of this issue isn't as huge as I thought it was. Small priority.