Reordered and cleaned up #includes in the engine.
Almost every file in the engine code was using spaces instead of tabs, which is now fixed. Also added some missing spaces in a couple of files.
Rewrote most of the engine using a much more object-oriented approach and using more of ScummVM's common classes. This design deviates quite a lot from the original engine's, but should be more maintainable and extensible in the future.