rogue: fix is_digit prototype

[Alexey Dobriyan <adobriyan_(_at_)_gmail_(_dot_)_com>]

Index: games/rogue//rogue.h
===================================================================
RCS file: /cvs/src/games/rogue/rogue.h,v
retrieving revision 1.15
diff -u -p -r1.15 rogue.h
--- games/rogue//rogue.h	2006/03/06 04:41:18	1.15
+++ games/rogue//rogue.h	2006/03/07 14:05:19
@@ -565,7 +565,7 @@ void	inv_armor_weapon(boolean);
 void	inv_rings(void);
 void	inventory(object *, unsigned short);
 boolean	is_all_connected(void);
-boolean	is_digit(int);
+boolean	is_digit(short);
 boolean	is_direction(short, short *);
 boolean	is_pack_letter(short *, unsigned short *);
 boolean	is_passable(short, short);