* The restriction on the parameter 'delta' was too strict, so we
  loosen it (delta only ever gets multiplied by -4, ... , 4,
  whereas beta gets multiplied by -7, ..., 7)
* Correct a comment about the border clamping
* Fix an issue with the test case

Change-Id: I30e55203455ba6e419b5a8b646151a6d1fd5cc3b