Make GdkDevice, GdkVisual objects

[Owen Taylor <otaylor redhat com>]

After some discussion with Paolo, Tim, and James yesterday, I
just filed this bug in bugzilla [ #56861 ]:

    GdkDevice and GdkVisual only vaguely fit the concept of what
    should be a boxed type. GdkVisual is immutable, GdkDevice
    isn't, they both are members of a fixed set and are not
    memory managed.

    In a language binding, you would expect to be able to write 
    something like:

    widget::get_colormap() == GtkColormap::get_system()

    But boxed types don't have a concept of preserving equality
    over a copy, so making this works forces the language
    binding to special case the equality operation for such
    types ... you won't have a persistant language object
    associated with the GDK object. Making a fixed association
    of language object <=> GDK object requires the features
    of GObject.

If someone has time to make up a patch for this in the short
term (API freeze tomorrow evening) timescale, that could
be useful.

Regards,
                                        Owen