[KWalletPasswords] Build only with Qt4.

Also show better error message when loading plugin fails

src/lib/plugins/plugins.cpp

@@ -132,8 +132,9 @@ void Plugins::loadPlugins()
     foreach (const QString &fullPath, m_allowedPlugins) {
         QPluginLoader* loader = new QPluginLoader(fullPath);
         PluginInterface* iPlugin = qobject_cast<PluginInterface*>(loader->instance());
+
         if (!iPlugin) {
-            qWarning() << "Plugins::loadPlugins" << loader->errorString();
+            qWarning() << "Plugins::loadPlugins Loading" << fullPath << "failed:" << loader->errorString();
             continue;
         }
 

src/plugins/plugins.pro

@@ -27,6 +27,7 @@ outOfDirPlugins = $$(QUPZILLA_PLUGINS_SRCDIR)
 
 # KWalletPasswords only with KDE_INTEGRATION
 !contains(DEFINES, KDE_INTEGRATION): SUBDIRS -= $$PWD/KWalletPasswords
+!lessThan(QT_VERSION, 5.0): SUBDIRS -= $$PWD/KWalletPasswords
 
 # GnomeKeyringPasswords only with GNOME_INTEGRATION
 !contains(DEFINES, GNOME_INTEGRATION): SUBDIRS -= $$PWD/GnomeKeyringPasswords