qml: allow enums as function parameters

See attached example:

What works: if I have an enum declared by Q_ENUMS, then in qml I can use its values (by ClassName.ENUM_ID):

Q_ENUMS(test_enum)
enum test_enum { ENUM1, ENUM2 };

console.log("TestClass.ENUM1 == " + TestClass.ENUM1);

returns:

TestClass.ENUM1 == 0

Similarly one can use enums for properties.

What does not work: if I have a public slot:

QString testFunction(test_enum)

then

console.log(instance.testFunction(TestClass.ENUM1));

gives an error:

test.qml:12: Error: Unknown method parameter type: test_enum

So the request is: please enable the last structure: please enable calling from qml slots which arguments are declared enums of classes registered by qmlRegisterType.