Input related generalisations

* Move key types into own file
* Use Generalized input methods in game.cpp

src/game.h

@@ -22,6 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "irrlichttypes_extrabloated.h"
 #include <string>
+#include "client/keys.h"
 #include "keycode.h"
 #include <list>