Clean up includes in the "classes" folder

- Canonicalized the header guards
- Removed all the sneaky dependencies between files
- Made sure includes were properly sorted

osx/classes.h

@@ -8,6 +8,8 @@
  *
  */
 
+// TODO: Delete this file, and move the function defined here to a more appropriate place.
+
 #include "simpletypes.h"
 #include "location.h"
 #include "terrain.h"