Solve some clazy warnings

My last patch triggered me to run clazy on the project. This patch
solves some of them:
- Proper iteration of some types, saving their copy.
- compile-time connects
- prefer using connects with the 3rd argument as an object when using
lambdas.

src/declarativeimports/core/tooltipdialog.cpp

@@ -26,7 +26,7 @@ ToolTipDialog::ToolTipDialog(QQuickItem  *parent)
 
     m_showTimer = new QTimer(this);
     m_showTimer->setSingleShot(true);
-    connect(m_showTimer, &QTimer::timeout, [ = ]() {
+    connect(m_showTimer, &QTimer::timeout, this, [this]() {
         setVisible(false);
     });
 }

src/plasma/pluginloader.cpp

@@ -121,9 +121,8 @@ PluginLoader::PluginLoader()
 
 PluginLoader::~PluginLoader()
 {
-    typedef QPointer<PackageStructure> pswp;
-    for (pswp wp : qAsConst(d->structures)) {
-        delete wp.data();
+    for (const auto &wp : qAsConst(d->structures)) {
+        delete wp;
     }
     delete d;
 }

src/plasmaquick/appletquickitem.cpp

@@ -596,7 +596,7 @@ void AppletQuickItem::init()
             reason = d->applet->launchErrorMessage();
         } else if (d->applet->kPackage().isValid()) {
             const auto errors = d->qmlObject->mainComponent()->errors();
-            for (QQmlError error : errors) {
+            for (const QQmlError &error : errors) {
                 reason += error.toString() + QLatin1Char('\n');
             }
             reason = i18n("Error loading QML file: %1", reason);

src/scriptengines/qml/plasmoid/containmentinterface.cpp

@@ -482,8 +482,8 @@ void ContainmentInterface::processMimeData(QMimeData *mimeData, int x, int y, KI
         job->setParent(m_dropMenu.data());
 
         QObject::connect(job, &KJob::result, this, &ContainmentInterface::dropJobResult);
-        QObject::connect(job, SIGNAL(mimetype(KIO::Job*, QString)),
-                this, SLOT(mimeTypeRetrieved(KIO::Job*,QString)));
+        QObject::connect(job, QOverload<KIO::Job *, const QString &>::of(&KIO::MimetypeJob::mimetype),
+                this, &ContainmentInterface::mimeTypeRetrieved);
 
     } else {
         bool deleteDropMenu = true;