Clang: Fix build with clang-8

Clang-Tidy checks and Clazy flags updated.
CLANG-UPGRADE-CHECK done.

Change-Id: I1ca585c5c3c77a7f183719df9c262603150914e8
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/tools/clangrefactoringbackend/source/symbolscollector.cpp

@@ -92,8 +92,9 @@ newFrontendActionFactory(Factory *consumerFactory,
                   m_sourceFileCallbacks(sourceFileCallbacks)
             {}
 
-            std::unique_ptr<clang::ASTConsumer>
-                    CreateASTConsumer(clang::CompilerInstance &instance, StringRef inFile) override {
+            std::unique_ptr<clang::ASTConsumer> CreateASTConsumer(clang::CompilerInstance &instance,
+                                                                  llvm::StringRef inFile) override
+            {
                 return m_consumerFactory->newASTConsumer(instance, inFile);
             }