The following problems in the interface of SvxCheckListBox (resp. its base
classes like SvTreeListBox) have been noted while implementing CWS jl49 (see the
three TODOs in desktop/source/deployment/gui/dp_gui_updatedialog.cxx:1.1.2.20 l.
718, l. 747, l. 931):

- To be practically useful, it has to be clear to a client when passed-in user
data is referenced by SvxCheckListBox and when not, esp. with regard to
exceptions thrown from functions like SetEntryData, RemoveEntry, or the extended
InsertEntry.

- InsertEntry should return something identifying the newly inserted entry, so
that for example checking that entry (CheckEntryPos) after insertion can be done
in a straightforward way, without first having to compute the correct position.

- It is strange that the entry positions in SvxCheckListBox are USHORT-based
while those of the underlying SvTreeListBox are ULONG-based.