C#: Extend the DB schema with a scoped annotation relation.

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -878,6 +878,13 @@ param_location(
   int id: @parameter ref,
   int loc: @location ref);
 
+@has_scoped_annotation = @local_scope_variable
+
+scoped_annotation(
+  int id: @has_scoped_annotation ref,
+  int kind: int ref // scoped ref = 1, scoped value = 2
+  );
+
 /** STATEMENTS **/
 
 @exprorstmt_parent = @control_flow_element | @top_level_exprorstmt_parent;