AutoTest: Code cosmetics

* use nullptr
* override
* remove old style casts
* fix most of the code model warnings

Change-Id: Ia08e846f9326ae28ca7e7d66748e25a8b817b9b1
Reviewed-by: Xing Xiong
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/autotestunittests.cpp

@@ -54,7 +54,7 @@ namespace Internal {
 AutoTestUnitTests::AutoTestUnitTests(TestTreeModel *model, QObject *parent)
     : QObject(parent),
       m_model(model),
-      m_tmpDir(0),
+      m_tmpDir(nullptr),
       m_isQt4(false)
 {
 }