fix github issue #134 - display of migrated objects

Fixes #134

An invisible hero (who can't see invisible and doesn't have autopickup
enabled) going down stairs to an object which fell down those stairs
will see the stairs instead of the object on them.  Missing newsym()
in obj_delivery() when objects aren't being passed through scatter().

src/explode.c

@@ -657,6 +657,7 @@ struct obj *obj; /* only scatter this obj        */
                 (void) break_statue(otmp);
                 place_object(otmp, sx, sy); /* put fragments on floor */
             }
+            newsym(sx, sy); /* in case it's beyond radius of 'farthest' */
             used_up = TRUE;
 
             /* 1 in 10 chance of destruction of obj; glass, egg destruction */