Removed an unused function declaration (fixes #1503)

* Function battle_validate_conf() does not exist.

src/map/battle.h

@@ -618,7 +618,6 @@ extern struct Battle_Config
 void do_init_battle(void);
 void do_final_battle(void);
 extern int battle_config_read(const char *cfgName);
-extern void battle_validate_conf(void);
 extern void battle_set_defaults(void);
 int battle_set_value(const char* w1, const char* w2);
 int battle_get_value(const char* w1);