C++: Add isThisAccess predicate to ParamAccessForType

cpp/ql/lib/semmle/code/cpp/exprs/Access.qll

@@ -394,6 +394,11 @@ class FunctionAccess extends Access, @routineexpr {
  */
 class ParamAccessForType extends Expr, @param_ref {
   override string toString() { result = "param access" }
+
+  /**
+   * Holds if the accessed parameter is implicit object parameter of the function.
+   */
+  predicate isThisAccess() { param_ref_to_this(underlyingElement(this)) }
 }
 
 /**

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -2040,6 +2040,10 @@ new_array_allocated_type(
     int type_id: @type ref
 );
 
+param_ref_to_this(
+    int expr: @param_ref ref
+)
+
 /**
  * The field being initialized by an initializer expression within an aggregate
  * initializer for a class/struct/union. Position is used to sort repeated initializers.