Disabling stash gold when buying items

Characters were previously able to access gold from the stash through
vendor screen.

This patch disables it, as in ironman you should not have access to any
stash.

Implements #30

Source/stores.cpp

@@ -350,7 +350,7 @@ void ScrollSmithBuy(int idx)
 
 uint32_t TotalPlayerGold()
 {
-	return MyPlayer->_pGold + Stash.gold;
+	return MyPlayer->_pGold + (IsIronman ? 0 : Stash.gold);
 }
 
 void StartSmithBuy()