AutoTest: Modernize code

* remove unnecessary QLatin1String where possible
* foreach
* nullptr
* bad naming of static members

Change-Id: If0f7c6839be4d2efbfef6f7f0775d2034775bd90
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/qtest/qttestvisitors.cpp

@@ -142,7 +142,7 @@ bool TestAstVisitor::visit(CPlusPlus::CallAST *ast)
 bool TestAstVisitor::visit(CPlusPlus::CompoundStatementAST *ast)
 {
     if (!ast || !ast->symbol) {
-        m_currentScope = 0;
+        m_currentScope = nullptr;
         return false;
     }
     m_currentScope = ast->symbol->asScope();