Some code cleanup, mainly constants

- Strip out unused constants
- Use const instead of #define
- Remove some obsolete comments

src/scenedit/scen.fileio.cpp

@@ -21,8 +21,6 @@
 #include "winutil.hpp"
 #include "choicedlog.hpp"
 
-#define	DONE_BUTTON_ITEM	1
-
 extern cScenario scenario;
 
 extern cTown* town;