C++: add upgrade and downgrade scripts

Author: IdrissRio

cpp/downgrades/08a2e59ed150d24b85a4fb2fc273edb8ad40e4a3/lambda_params.ql

@@ -0,0 +1,9 @@
+class LambdaExpr extends @lambdaexpr {
+  string toString() { none() }
+}
+
+from
+  LambdaExpr lambda, string default_capture, boolean has_explicit_return_type,
+  boolean has_explicit_parameter_list
+where lambdas(lambda, default_capture, has_explicit_return_type, has_explicit_parameter_list, _)
+select lambda, default_capture, has_explicit_return_type, has_explicit_parameter_list