Schroedinger's live cat

Give a little experience when releasing live housecat from Schroedinger's
Box, similar to recent change giving experience when opening the Box
produces a dead cat.

src/pickup.c

@@ -2857,6 +2857,13 @@ observe_quantum_cat(struct obj *box, boolean makecat, boolean givemsg)
             }
             box->owt = weight(box);
             box->spe = 0;
+
+            if (!svc.context.mon_moving) {
+                /* give experience points for releasing live cat; slightly
+                   different amount from what is given for "killing" it */
+                more_experienced(10, 20); /* 10:current exp; 20:score bonus */
+                newexplevel();
+            }
         }
     } else {
         box->spe = 0; /* now an ordinary box (with a cat corpse inside) */