[PATCH 2/2] comctl32/listbox: Implement LBS_NODATA

[Gabriel Ivăncescu]

I forgot to mention: besides the bug report, a real life use case at
least for single-selection listboxes is Wine's own autocomplete
implementation in the very near future.

I plan to convert it to use LBS_NODATA (once it's implemented) for a
40% performance gain on large suggestions, so that it is much more
manageable on a large enumeration (virtual database fs for instance).

Obviously it has to be implemented first or there's no point at all.
(and yes, the "special cases" everywhere needs to remain for
single-selection listboxes)