Use enums for most of the rest of the game constants.

This adds an "enum map" type that allows safe usage of an enum to index an array.
(That is, it enforces that the index is of the enum type.)

src/game/boe.graphics.hpp

@@ -23,7 +23,7 @@ void reload_startup();
 void draw_startup(short but_type);
 void draw_anim();
 void place_anim(); 
-void draw_start_button(short which_position,short which_button);
+void draw_start_button(eStartButton which_position,short which_button);
 void main_button_click(int which_button);
 void arrow_button_click(rectangle button_rect);
 void end_startup();