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/plugins/clangrefactoring/sourcelocations.h

@@ -50,6 +50,13 @@ public:
         Utils::PathString sourcePath;
     };
 
+    enum LocationGetter
+    {
+        SourceId = 0,
+        Line,
+        Column
+    };
+
     std::vector<Location> locations;
     std::unordered_map<qint64, Utils::PathString> sources;
 };