Fix gcc build and rendering of map tiles

Object renderables like the Avatar and NPCs are still broken though.
Fix Animation::getCurrentFrame()

There's still the issue of returning a reference to a local variable.
Perhaps adding a dummy Renderable to the Animation class would take care
of that?
Fix local var reference with dummy Renderable in Animation class
Merge pull request #6 from dorkster/render_refactor

Fixing those FIXMEs