[9957] Alow sell item for money and extanded coset without momey in same time.

npc_vendor.ExtandedCost can be negative now that meaning:
price excluded default item BuyPrice and use only abs(ExtandedCost) items).
For example expected used for item 36908.

src/game/Level2.cpp

@@ -1129,7 +1129,7 @@ bool ChatHandler::HandleNpcAddVendorItemCommand(const char* args)
         incrtime = atol(fincrtime);
 
     char* fextendedcost = strtok(NULL, " ");                //add ExtendedCost, default: 0
-    uint32 extendedcost = fextendedcost ? atol(fextendedcost) : 0;
+    int32 extendedcost = fextendedcost ? atol(fextendedcost) : 0;
 
     Creature* vendor = getSelectedCreature();