Fix pile display when picking up items while invisible

Reported directly to the devteam. Set hilite_pile on, become
invisible, pick up all but one item from a pile on the floor,
the pile symbol was still there afterwards.

This is yet another case of evil hack, because the gbuf doesn't
distinguish between object piles and single items, see
commit 854fe40609

src/pickup.c

@@ -707,7 +707,7 @@ int what; /* should be a long */
 
         /* position may need updating (invisible hero) */
         if (n_picked)
-            newsym(u.ux, u.uy);
+            newsym_force(u.ux, u.uy);
 
         /* check if there's anything else here after auto-pickup is done */
         if (autopickup)