Use wxControl instead of wxControlWithItems with wxRTTI macros.

Use wxControl instead of wxControlWithItems with wxRTTI macros.

wxControlWithItems is just a convenient combination of wxControl and
wxItemContainer mix-in and it is not useful to include it in wxRTTI classes
hierarchy. Also, using wxControlWithItems as the base class for wxChoice and
wxListBox but not for wxComboBox is inconsistent but wxControlWithItems can't
be used for the latter so resolve this by not using it at all.

Ideally we'd have a way of retrieving the list of supported interfaces (such
as wxItemContainer or wxTextEntry) via wxRTTI too.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66574 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775