Remove CENT-output free transaction rule when relaying

Remove the (relay/mempool) rule that all outputs of free transactions
must be greater than 0.01 XBT. Dust spam is now taken care of by making
dusty outputs non-standard.

src/wallet.cpp

@@ -1232,9 +1232,10 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64> >& vecSend,
                 }
 
                 int64 nChange = nValueIn - nValue - nFeeRet;
-                // if sub-cent change is required, the fee must be raised to at least nMinTxFee
-                // or until nChange becomes zero
-                // NOTE: this depends on the exact behaviour of GetMinFee
+                // The following if statement should be removed once enough miners
+                // have upgraded to the 0.9 GetMinFee() rules. Until then, this avoids
+                // creating free transactions that have change outputs less than
+                // CENT bitcoins.
                 if (nFeeRet < CTransaction::nMinTxFee && nChange > 0 && nChange < CENT)
                 {
                     int64 nMoveToFee = min(nChange, CTransaction::nMinTxFee - nFeeRet);