using the specified @a fnSortCallBack function. This function must have the
following prototype:
@code
- int wxCALLBACK wxListCompareFunction(long item1, long item2, wxIntPtr sortData)
+ int wxCALLBACK wxListCompareFunction(wxIntPtr item1, wxIntPtr item2, wxIntPtr sortData)
@endcode
It is called each time when the two items must be compared and should return 0