C++: Add predicates for lambda parameter list

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

@@ -48,6 +48,19 @@ class LambdaExpression extends Expr, @lambdaexpr {
    */
   predicate returnTypeIsExplicit() { lambdas(underlyingElement(this), _, true, _) }
 
+  /**
+   * Holds if the lambda has an explicitly specified parameter list, even when empty.
+   */
+  predicate hasParameterList() { lambdas(underlyingElement(this), _, _, true) }
+
+  /**
+   * Holds if the lambda has an empty parameter list
+   */
+  predicate emptyParameterListIsExplicit() {
+    this.hasParameterList() and
+    this.getLambdaFunction().getNumberOfParameters() = 0
+  }
+
   /**
    * Gets the function which will be invoked when the resulting object is called.
    *