Resolve ambiguity between GetClientXXX() methods in wxOSX wxComboBox.

Use wxCONTROL_ITEMCONTAINER_CLIENTDATAOBJECT_RECAST for wxOSX/Cocoa too, not
only for wxOSX/Carbon. This macro adds methods to explicitly disambiguate
between the two inherited versions of each GetClientXXX() method, the one from
wxItemContainer and the other one from wxEvtHandler.

Closes #11637.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68459 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/combobox.h

@@ -144,9 +144,7 @@ class WXDLLIMPEXP_CORE wxComboBox :
 
     virtual bool        OSXHandleClicked( double timestampsec );
 
-#if wxOSX_USE_CARBON
     wxCONTROL_ITEMCONTAINER_CLIENTDATAOBJECT_RECAST
-#endif
 
 #if wxOSX_USE_COCOA
     wxComboWidgetImpl* GetComboPeer() const;