Avoid implicit declaration of the Move_point function in
Wall_in_between_points in suibotdef.c.

diff --git a/src/server/server.h b/src/server/server.h
index 5c0cdd66de1db008..30b7f7d0a8fb09e4 100644
--- a/src/server/server.h
+++ b/src/server/server.h
@@ -151,6 +151,8 @@ void Groups_init(void);
 void Walls_init(void);
 void Treasure_init(void);
 void Move_init(void);
+struct collans;
+void Move_point(const move_t *move, struct collans *answer);
 void Move_object(object_t *obj);
 void Move_player(player_t *pl);
 void Turn_player(player_t *pl, bool push);