Fixed KWMessagePattern not matching class arguments.

The test below fails with the current code, due to KWMessagePattern encoding Class as NSData and evaluating it with equalsTo:.

```objc
it(@"Recognizes params with classes",^{
 +        NSMutableArray *array = [NSMutableArray array];
 +        [[[array should] receive] isKindOfClass:[NSArray class]];
 +        [array isKindOfClass:[NSArray class]];
 +    });
```

The fix adds an extra KWObjCTypeIsClass() check.

I've also removed two -fno-objc-arc declarations from the Kiwi-OSX target, as the files are currently written for ARC and were causing on OSX unit tests.