matekbd-keyboard-drawing: Prevent gtk+ keynav from taking focus away
matekbd-keyboard-drawing: Prevent gtk+ keynav from taking focus away

We need to tell gtk+ we handled the key event otherwise gtk+ keynav
key events will move focus to the close button and it looks like the
dialog stopped working.

taken from:
https://git.gnome.org/browse/libgnomekbd/commit/?id=648cd5a

mate-desktop/libmatekbd,mate-desktop/libmatekbd