Have each game declare a name which is used for window titles etc.

[originally from svn r4167]

puzzles.h

@@ -93,6 +93,7 @@ void random_free(random_state *state);
 /*
  * Game-specific routines
  */
+extern const char *const game_name;
 game_params *default_params(void);
 int game_fetch_preset(int i, char **name, game_params **params);
 void free_params(game_params *params);