Fix function prototype warnings for C23 compatibility

- Add proper function prototypes: fatal(), my_exit(), set_order()
- Fix function pointer types to match call sites: void (*func)(int)
- Remove conflicting localtime() declaration in rip.c
- Fix incorrect new_item() call in state.c (remove unused argument)

Result: Zero compilation warnings, C23 compatible.

See MODERNIZATION_LOG.md for detailed analysis.

extern.h

@@ -131,11 +131,11 @@ void	come_down();
 void	doctor();
 void	end_line();
 void    endit(int sig);
-void	fatal();
+void	fatal(char *s);
 void	getltchars();
 void	land();
 void    leave(int);
-void	my_exit();
+void	my_exit(int st);
 void	nohaste();
 void	playit();
 void    playltchars(void);
@@ -144,7 +144,7 @@ void    quit(int);
 void    resetltchars(void);
 void	rollwand();
 void	runners();
-void	set_order();
+void	set_order(int *order, int numthings);
 void	sight();
 void	stomach();
 void	swander();