Problem with isAssignable in IOSConcreteClass.m

isAssignable doesn't work when testing assignable on the interface implementation. Perhaps, it uses isAssignable in IOSConcreteClass.m. It seems to use isSubclass which is not giving the expected behavior when the class conforms a protocol.

I think this may only happens with XCode9-Swift4 update as my code broken after upgrading to it. Please see below code to see the difference between isAssignable in Java and Swift 4.

Thank you for your help in advance!

**In Java**
```
// print "Can Arraylist -> List? true"
System.out.println("Can Arraylist -> List? " + List.class.isAssignableFrom(ArrayList.class));
```

**In Swift4 (XCode 9)**
```
// print false -- Protocol conformance is somehow not assignable (problem here)
print(JavaUtilList_class_().isAssignable(from: JavaUtilArrayList_class_()))

// print true -- Subclass seems to work fine
print(JavaUtilAbstractCollection_class_().isAssignable(from: JavaUtilArrayList_class_()))

// print true
print(JavaUtilArrayList_class_().objcClass.conforms(to: JavaUtilList.self))

// print false
print(JavaUtilArrayList_class_().objcClass.isSubclass(of: JavaUtilList.self))
```