wxOSX/Carbon compilation fix after wxListBoxBase changes.

Making wxListBoxBase::CalcAndSendEvent() broke wxOSX/Carbon build, fix it by
making the class which needs to call it friend of wxListBox in this port.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65940 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/listbox.h

@@ -168,6 +168,11 @@ protected:
     wxArrayPtrVoid m_itemsClientData;
 
 private:
+#ifdef __WXOSX_CARBON__
+    // It needs to call our CalcAndSendEvent().
+    friend class wxMacDataBrowserListControl;
+#endif // Carbon
+
     DECLARE_DYNAMIC_CLASS(wxListBox)
     DECLARE_EVENT_TABLE()
 };