1. the main function for item insertion is now DoInsertItems() which allows
for much more efficient addition of many new items at once
2. the items client data management is done entirely in wxItemContainer
itself, the derived classes don't have to distinguish between void and
object client data
3. many fixes for sorted controls, in particular implemented wxCB_SORT support
in wxGTK combobox
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47730 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
