Show zero value txouts in listunspent.

It's reasonable that automatic coin selection will not pick a zero
 value txout, but they're actually  spendable; and you should know
 if you have them. Listing also makes them available to tools like
 dust-b-gone.

src/wallet/rpcwallet.cpp

@@ -2301,7 +2301,7 @@ Value listunspent(const Array& params, bool fHelp)
     vector<COutput> vecOutputs;
     assert(pwalletMain != NULL);
     LOCK2(cs_main, pwalletMain->cs_wallet);
-    pwalletMain->AvailableCoins(vecOutputs, false);
+    pwalletMain->AvailableCoins(vecOutputs, false, NULL, true);
     BOOST_FOREACH(const COutput& out, vecOutputs) {
         if (out.nDepth < nMinDepth || out.nDepth > nMaxDepth)
             continue;

src/wallet/wallet.cpp

@@ -1481,7 +1481,7 @@ CAmount CWallet::GetImmatureWatchOnlyBalance() const
 /**
  * populate vCoins with vector of available COutputs.
  */
-void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const CCoinControl *coinControl) const
+void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const CCoinControl *coinControl, bool fIncludeZeroValue) const
 {
     vCoins.clear();
 
@@ -1508,7 +1508,7 @@ void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const
             for (unsigned int i = 0; i < pcoin->vout.size(); i++) {
                 isminetype mine = IsMine(pcoin->vout[i]);
                 if (!(IsSpent(wtxid, i)) && mine != ISMINE_NO &&
-                    !IsLockedCoin((*it).first, i) && pcoin->vout[i].nValue > 0 &&
+                    !IsLockedCoin((*it).first, i) && (pcoin->vout[i].nValue > 0 || fIncludeZeroValue) &&
                     (!coinControl || !coinControl->HasSelected() || coinControl->IsSelected((*it).first, i)))
                         vCoins.push_back(COutput(pcoin, i, nDepth, (mine & ISMINE_SPENDABLE) != ISMINE_NO));
             }

src/wallet/wallet.h

@@ -540,7 +540,7 @@ public:
     //! check whether we are allowed to upgrade (or already support) to the named feature
     bool CanSupportFeature(enum WalletFeature wf) { AssertLockHeld(cs_wallet); return nWalletMaxVersion >= wf; }
 
-    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlyConfirmed=true, const CCoinControl *coinControl = NULL) const;
+    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlyConfirmed=true, const CCoinControl *coinControl = NULL, bool fIncludeZeroValue=false) const;
     bool SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int nConfTheirs, std::vector<COutput> vCoins, std::set<std::pair<const CWalletTx*,unsigned int> >& setCoinsRet, CAmount& nValueRet) const;
 
     bool IsSpent(const uint256& hash, unsigned int n) const;