Deprecated `object.selector`

The public import of `selector` in the module `object` has been deprecated.
Please explicitly import `selector` instead using: `import core.attribute : selector;`

The following code has been deprecated:

```
extern (Objective-C)
extern class NSObject
{
    static NSObject alloc() @selector("alloc");
}
```

Replace with:

```
import core.attribute : selector;

extern (Objective-C)
extern class NSObject
{
    static NSObject alloc() @selector("alloc");
}
```
