[Lazarus] OwnerData ListView

[Hans-Peter Diettrich]

I've just uploaded an patch for the proper implementation of virtual 
listviews. Major problem was to make AllocBy used instead of the 
ListItems count.

The updated examples/listview project now allows to switch between 
normal and virtual mode, and can be used to test the implementation and 
behaviour on other widgetsets (tested with Win32 only).

DoDi