Allow dimming and hiding specific entries in ring controls

[Wolfgang]

I made this suggestion some time ago - unfortunately I had combined it with another, related idea. The other idea was implemented so now the complete issue is dead, sorry, completed.

This suggestion is meant to revive the unfulfilled request of two new attributes, allowing to dim and hide a specified entry in a ring control. This would be convenient as it avoids to programmatically rebuild the control.

Thanks!