Fix priority calculation in CreateTransaction

Make this projection of priority in 1 block match the calculation in the low priority reject code.

src/wallet.cpp

@@ -1439,10 +1439,14 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, CAmount> >& vecSend,
                 BOOST_FOREACH(PAIRTYPE(const CWalletTx*, unsigned int) pcoin, setCoins)
                 {
                     CAmount nCredit = pcoin.first->vout[pcoin.second].nValue;
-                    //The priority after the next block (depth+1) is used instead of the current,
+                    //The coin age after the next block (depth+1) is used instead of the current,
                     //reflecting an assumption the user would accept a bit more delay for
                     //a chance at a free transaction.
-                    dPriority += (double)nCredit * (pcoin.first->GetDepthInMainChain()+1);
+                    //But mempool inputs might still be in the mempool, so their age stays 0
+                    int age = pcoin.first->GetDepthInMainChain();
+                    if (age != 0)
+                        age += 1;
+                    dPriority += (double)nCredit * age;
                 }
 
                 CAmount nChange = nValueIn - nValue - nFeeRet;