Clang: Update symbol database if file has changed

The code in the symbol indexer is quite similar, but still different
enough to prevent easy reuse of the function.

Change-Id: I47907d90066da922eafe8ff3cce124ea47ea4a0a
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/tools/clangrefactoringbackend/source/symbolindexer.h

@@ -50,6 +50,7 @@ public:
 
     void pathsWithIdsChanged(const Utils::SmallStringVector &ids) override;
     void pathsChanged(const FilePathIds &filePathIds) override;
+    void updateChangedPath(FilePathId filePath);
 
 private:
     SymbolsCollectorInterface &m_symbolsCollector;