Don't copy array for BatArray.backwards enum clone

This will make it faster and enable value sharing.
Without sharing a change to the original array would be visible in the
original backwards enum, but not in its clone. This certainly is not the
expected behaviour.

See commit 8944b0d30b5d062e2f01f5bd9e73e5a9718c5a51
Merge pull request #351 from madroach/master

Change BatArray.backwards to match