cocoa.messages: Add a Cocoa union type to import NSData.
cocoa.messages: Add a Cocoa union type to import NSData.

Fixes bootstrap for macOS 10.14 for the error:
```
no-objc-type
name "("
```

Fixes #2059.

factor/factor,AlexIljin/factor,bpollack/factor,bpollack/factor,tgunr/factor,AlexIljin/factor,mrjbq7/factor,mrjbq7/factor,bpollack/factor,factor/factor,mrjbq7/factor,AlexIljin/factor,mrjbq7/factor,bpollack/factor,tgunr/factor,AlexIljin/factor,bpollack/factor,bpollack/factor,AlexIljin/factor,AlexIljin/factor,AlexIljin/factor,factor/factor,factor/factor,mrjbq7/factor,tgunr/factor,tgunr/factor,factor/factor,bpollack/factor,tgunr/factor,factor/factor,mrjbq7/factor,tgunr/factor