TrkExAlgs: Fix compilation with clang.

Gaudi property conversion.
Missing override keyword.

Tracking/TrkExtrapolation/TrkExAlgs/TrkExAlgs/PropResultRootWriterSvc.h

@@ -33,7 +33,7 @@ class PropResultRootWriterSvc : public AthService {
       return IID_PropResultRootWriterSvc;    
     }
     
-    virtual StatusCode queryInterface(const InterfaceID& riid, void** ppvInterface) {
+    virtual StatusCode queryInterface(const InterfaceID& riid, void** ppvInterface) override {
       ATH_MSG_DEBUG("in queryInterface()");    
       if (PropResultRootWriterSvc::interfaceID().versionMatch(riid)) {
         ATH_MSG_DEBUG("matched PropResultRootWriterSvc");

Tracking/TrkExtrapolation/TrkExAlgs/src/PropResultRootWriterSvc.cxx

@@ -29,7 +29,7 @@ StatusCode Trk::PropResultRootWriterSvc::initialize()
   const std::string treeName = m_treeName;  
   m_tree = new TTree(treeName.data(), "MyStudies");
   
-  std::string fullNtupleName = m_ntupleDirName + m_treeName;
+  std::string fullNtupleName = static_cast<std::string>(m_ntupleDirName) + m_treeName;
   CHECK(m_thistSvc->regTree(fullNtupleName, m_tree));
 
   if(m_tree == nullptr) {