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.items.cpp

@@ -26,8 +26,9 @@
 #include "winutil.hpp"
 #include "cursors.hpp"
 
-extern short stat_window,which_combat_type;
+extern short which_combat_type;
 extern eGameMode overall_mode;
+extern eItemWinMode stat_window;
 extern sf::RenderWindow mainPtr;
 extern bool boom_anim_active;
 extern rectangle d_rects[80];