fix #K3514 - unpaid_cost() impossible

Fix the reported bug of using Passes_walls to carry an unpaid item
from inside a shop into the wall it shares with another shop
producing a situation where examining inventory issued an impossible
"unpaid_cost: object wasn't on any bill" when trying to append the
cost to the formatted inventory line.  u.ushops[], u.ushops0[], and
others are lists that can have up to four entries and the relevant
code was only checking the first one.

Not mentioned in the report:  continuing another step into the other
shop didn't get recognized as robbing the first shop, for a similar
reason.

For either of these bugs, digging a breach in the wall, paying off
the miffed shopkeeper, then stepping into the breach before it gets
repaired will probably trigger the same results without the need for
polymorphing into a xorn or earth elemental.  But not on the tourist
goal level test case since walls there are undiggable.

I didn't go looking for other instances of not checking all relevant
shopkeepers.  It wouldn't surprise me if there are some more.

doc/fixes37.0

@@ -738,6 +738,13 @@ getting wounded in one leg when the other was already wounded miraculously
 when parsing config file entry "BINDINGS=key1:cmd1,key2:cmd2,key3:cmd3" allow
 	keyN to be either a naked comma or backslash+comma instead requiring
 	that comma's numeric value be used to bind comma to a command
+when two or more shops share a wall and hero uses Passes_walls to carry an
+	unpaid item from inside a shop into the shared wall, it could yield
+	impossible "unpaid_cost: object wasn't on any bill" when examining
+	inventory if the shop code picked wrong shopkeeper to determine cost
+when two or more shops share a wall and hero uses Passes_walls to carry an
+	unpaid item through the shared wall into another shop, theft of that
+	unpaid item from the first shop wasn't noticed
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/shk.c

@@ -385,7 +385,7 @@ inside_shop(register xchar x, register xchar y)
 }
 
 void
-u_left_shop(char* leavestring, boolean newlev)
+u_left_shop(char *leavestring, boolean newlev)
 {
     struct monst *shkp;
     struct eshk *eshkp;
@@ -400,7 +400,7 @@ u_left_shop(char* leavestring, boolean newlev)
     if (!*leavestring && (!levl[u.ux][u.uy].edge || levl[u.ux0][u.uy0].edge))
         return;
 
-    shkp = shop_keeper(*u.ushops0);
+    shkp = shop_keeper(*leavestring ? *leavestring : *u.ushops0);
     if (!shkp || !inhishop(shkp))
         return; /* shk died, teleported, changed levels... */
 
@@ -2422,19 +2422,20 @@ unpaid_cost(
     struct bill_x *bp = (struct bill_x *) 0;
     struct monst *shkp;
     long amt = 0L;
+
+#if 0   /* if two shops share a wall, this might find wrong shk */
     xchar ox, oy;
 
     if (!get_obj_location(unp_obj, &ox, &oy, BURIED_TOO | CONTAINED_TOO))
         ox = u.ux, oy = u.uy; /* (shouldn't happen) */
     if ((shkp = shop_keeper(*in_rooms(ox, oy, SHOPBASE))) != 0) {
         bp = onbill(unp_obj, shkp, TRUE);
-    } else {
+    } else /* didn't find shk?  try searching bills */
-        /* didn't find shk?  try searching bills */
+#endif
-        for (shkp = next_shkp(fmon, TRUE); shkp;
+    for (shkp = next_shkp(fmon, TRUE); shkp;
-             shkp = next_shkp(shkp->nmon, TRUE))
+         shkp = next_shkp(shkp->nmon, TRUE))
-            if ((bp = onbill(unp_obj, shkp, TRUE)) != 0)
+        if ((bp = onbill(unp_obj, shkp, TRUE)) != 0)
-                break;
+            break;
-    }
 
     /* onbill() gave no message if unexpected problem occurred */
     if (!shkp || (unp_obj->unpaid && !bp)) {