function on the call stack.

This is a consequence of Five integration which uses ZTC. To locate the
disabled test grep for the string "DISABLED".

- Fixed Shared.DC.ZRDB.{RDB|Results} to behave nicely with the new-style extensionclass
- Added a minimal test

Note that doctest support is not done yet!

        ip-address is unset

      - Use 'del' instead of 'list.remove()' in
        Catalog.delColumn(). There can be only one column with the
        same name, and it could potentially break catalog metadata as
        remove() may remove more than one element from the list if
        they have the same value. Also, we already have the list index
        we are interested in deleting so it doesn't make sense to look
        up the value and call 'list.remove()' on it.

getlocale() returns a tuple here. The original test author obviously saw a
list returned so I'll explicitly tuplify to be on the safe side...

- fix for collector #1721

        listings did not work)