NSArray is missing some properties

[stuartmorgan-g]

The generated NSArray in objective_c is missing at least firstObject and lastObject.

[liamappelbe]

These are probably part of an undocumented category. A lot of the core APIs put methods on categories that the official documentation says are part of the core interface.

[liamappelbe]

Yeah, these methods are part of NSExtendedArray.

I wonder if it'd make the package:objective_c bindings more readable if I inline all its category methods into the classes. I'd only do this for package:objective_c, because so many of these internal categories are undocumented.