removing non-working things

[Matthias Clasen <mclasen redhat com>]

The gnome-ui-properties capplet contains a "Detachable toolbars"
checkbox, which has three issues:

a) It only affects BonoboToolbars, not for regular GtkToolbars

b) It does not even work correctly for bonobo toolbars (try
   detaching and reattaching the evolution toolbar, for instance)

c) Even if it worked correctly everywhere, it is not a very
   useful feature.

So I'd like to propose that we drop this checkbox. 

If there is a need to fill the void, we could add a "Show icons in
buttons" checkbox instead, since this is a feature that works reliably
everywhere...

Matthias