Array(array) returns a copy instead of array itself

``` ruby
[1] pry(main)> arr = [1]
=> [1]
[3] pry(main)> arr.equal? Array(arr)
=> false
```

The commit that introduced the change: 0ed823a

MRI returns the same object on `Array(arr)`, `arr.to_a` and `arr.to_ary` when arr is an Array.
JRuby returns a copy in the first case.
