Fix and enhance support for client data in wxRibbonButtonBar.

Add the possibility to retrieve the client data associated with a button and
not only set it (which wasn't very useful on its own).

Also allow having both typed (owned) and untyped (not owned) client data, as
in the other wxWidgets controls.

To avoid confusion between two different kinds of data, remove "client_data"
argument from the functions adding buttons and provide separate methods with
distinct names for setting and getting client data.

Closes #14630.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72529 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -548,6 +548,9 @@ All (GUI):
 - Add expand/collapse button to wxRibbonBar (rakeshthp).
 - Fix item data access in wxDataViewListCtrl (Kry).
 - Fix problem with floating maximized AUI panes (Laurent Poujoulat).
+- Add owned client data support to wxRibbonButtonBar. Notice that the client
+  data now must be set using the SetItemClient{Data,Object}() methods and not
+  when inserting the button (Laurent Poujoulat).
 - Add wxBitmapButton::NewCloseButton().
 - Add wxTextEntry::SelectNone() (troelsk).
 - Restore the original wxGrid col/row size when unhiding it (Michael Richards).