Disable KeyBindingManager on right Alt keydown.

This fixes issue #8666.
No, what you interpret is wrong. Once you release AltGr key, a keyup event for Ctrl key is sent just like Ctrl key event is sent when you press AltGr key. When using AltGr key, you don't need to press Ctrl key at all. If you do, that can be considered as not using the AltGr shortcuts available for that specific keyboard layout.