LinGui: work around bonehead Gtk developer decision
The width of radio buttons in GtkStackSwitcher are hard coded to 100.
Parse the container to get the buttons and fix this idiocy.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6194 b64f7644-9d1e-0410-96f1-a4d463321fa5