Remove CWalletTx::vfSpent

Use the spent outpoint multimap to figure out which wallet transaction
outputs are unspent, instead of a vfSpent array that is saved
to disk.

src/qt/walletmodel.cpp

@@ -501,6 +501,12 @@ void WalletModel::getOutputs(const std::vector<COutPoint>& vOutpoints, std::vect
     }
 }
 
+bool WalletModel::isSpent(const COutPoint& outpoint) const
+{
+    LOCK(wallet->cs_wallet);
+    return wallet->IsSpent(outpoint.hash, outpoint.n);
+}
+
 // AvailableCoins + LockedCoins grouped by wallet address (put change in one group with wallet address)
 void WalletModel::listCoins(std::map<QString, std::vector<COutput> >& mapCoins) const
 {