3497. [func] When deleting a slave/stub zone using 'rndc delzone'

3497.   [func]          When deleting a slave/stub zone using 'rndc delzone'
                        report the files that were being used so they can
                        be cleaned up if desired. [RT #27899]

Squashed commit of the following:

commit 0e4e69d0c3153fe94aaa375b908cf7e3e45b5059
Author: Mark Andrews <marka@isc.org>
Date:   Thu Feb 21 17:01:44 2013 +1100

    report the zones to be removed rather than removing them

commit 5d247ac592eef64c4c467d99af4983b8c1ff998f
Author: Mark Andrews <marka@isc.org>
Date:   Wed Feb 20 15:05:47 2013 +1100

    remove slave/stub files when deleting a zone using delzone