C#: Add attribute kind to the dbscheme for the attribute relation.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/Attribute.qll

@@ -50,10 +50,10 @@ class Attributable extends @attributable {
  */
 class Attribute extends TopLevelExprParent, @attribute {
   /** Gets the type of this attribute. */
-  Class getType() { attributes(this, getTypeRef(result), _) }
+  Class getType() { attributes(this, _, getTypeRef(result), _) }
 
   /** Gets the element that this attribute is attached to. */
-  Attributable getTarget() { attributes(this, _, result) }
+  Attributable getTarget() { attributes(this, _, _, result) }
 
   /**
    * Gets the `i`th argument of this attribute. This includes both constructor

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -520,9 +520,17 @@ tuple_element(
 
 attributes(
   unique int id: @attribute,
+  int kind: int ref,
   int type_id: @type_or_ref ref,
   int target:  @attributable ref);
 
+case @attribute.kind of
+  0 = @attribute_default
+| 1 = @attribute_return
+| 2 = @attribute_assembly
+| 3 = @attribute_module
+;
+
 attribute_location(
   int id: @attribute ref,
   int loc: @location ref);