Clang: Add Symbol Indexing

It is a first step and now a database is generated if you start QtCreator.
Some code is now shared with the PchManager which can be improved in the
future.

Change-Id: Ic267fe7960f6c455d91832859a673ce98f269aa2
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/tools/clangrefactoringbackend/source/symbolstorage.h

@@ -27,9 +27,12 @@
 
 #include "symbolstorageinterface.h"
 
+#include <sqliteexception.h>
 #include <sqlitetransaction.h>
 #include <stringcache.h>
 
+#include <mutex>
+
 namespace ClangBackEnd {
 
 template <typename StatementFactory>
@@ -42,7 +45,7 @@ class SymbolStorage : public SymbolStorageInterface
 
 public:
     SymbolStorage(StatementFactory &statementFactory,
-                  FilePathCache<> &filePathCache)
+                  FilePathCache<std::mutex> &filePathCache)
         : m_statementFactory(statementFactory),
           m_filePathCache(filePathCache)
     {
@@ -149,7 +152,7 @@ public:
 
 private:
     StatementFactory &m_statementFactory;
-    FilePathCache<> &m_filePathCache;
+    FilePathCache<std::mutex> &m_filePathCache;
 };
 
 } // namespace ClangBackEnd