[Bug] Static class method cannot be used as callback

```
ERROR AS218: Cannot access method 'compare' without calling it as it requires 'this' to be set.

     actual.sort(Buffer.compare);
                 ~~~~~~~~~~~~~~
 in tests/buffer.spec.ts(60,16)
```

Thoughts?

EDIT: Found here: https://github.com/AssemblyScript/node/pull/7