Bugfix: Correct English grammar regarding "'s"

src/qt/bitcoin.cpp

@@ -299,7 +299,7 @@ int main(int argc, char *argv[])
                 window.setWalletModel(0);
                 guiref = 0;
             }
-            // Shutdown the core and it's threads, but don't exit Bitcoin-Qt here
+            // Shutdown the core and its threads, but don't exit Bitcoin-Qt here
             Shutdown(NULL);
         }
         else

src/qt/bitcoingui.cpp

@@ -492,7 +492,7 @@ void BitcoinGUI::setNumConnections(int count)
 
 void BitcoinGUI::setNumBlocks(int count, int nTotalBlocks)
 {
-    // don't show / hide progressBar and it's label if we have no connection(s) to the network
+    // don't show / hide progressBar and its label if we have no connection(s) to the network
     if (!clientModel || clientModel->getNumConnections() == 0)
     {
         progressBarLabel->setVisible(false);

src/qt/bitcoinunits.cpp

@@ -99,7 +99,7 @@ QString BitcoinUnits::format(int unit, qint64 n, bool fPlus)
     QString quotient_str = QString::number(quotient);
     QString remainder_str = QString::number(remainder).rightJustified(num_decimals, '0');
 
-    // Right-trim excess 0's after the decimal point
+    // Right-trim excess zeros after the decimal point
     int nTrim = 0;
     for (int i = remainder_str.size()-1; i>=2 && (remainder_str.at(i) == '0'); --i)
         ++nTrim;