[shell] Implement Texture_Tester
[vis] Default lighting is 1/1/1 now, not 1/0/1
[shell world] Add a real tileset, under construction
[hacc] X::Null_Pointer shouldn't infinite-loop on construction.
[hacc] Load special filetypes at prepare phase
[core] Don't hacc::file_transaction around before_next_frame
[shell] Open window before doing absolutely anything else.