several small Qt-related fixes

- make BitcoinGUI::showPaymentACK() use a reference for msg and use our
  own GUIUtil::HtmlEscape() function
- ensure QTimer usage in clientmodel is the same as in walletmodel
- remove an unneeded debug message in walletframe
- flag some parameters as unused in DebugMessageHandler()
- small code formatting changes

src/qt/bitcoin.cpp

@@ -155,11 +155,14 @@ static void initTranslations(QTranslator &qtTranslatorBase, QTranslator &qtTrans
 #if QT_VERSION < 0x050000
 void DebugMessageHandler(QtMsgType type, const char * msg)
 {
+    Q_UNUSED(type);
     LogPrint("qt", "Bitcoin-Qt: %s\n", msg);
 }
 #else
 void DebugMessageHandler(QtMsgType type, const QMessageLogContext& context, const QString &msg)
 {
+    Q_UNUSED(type);
+    Q_UNUSED(context);
     LogPrint("qt", "Bitcoin-Qt: %s\n", qPrintable(msg));
 }
 #endif