[Vala] Warnings when subclassing classes without public constructor

[Mike Massonnet <mmassonnet gmail com>]

Hello,

I had like to know if there exists a way to avoid a warning when
compiling with valac classes that subclass classes without public
constructors. As an example, Gtk.Bin doesn't have any public
constructor but it is still valid to subclass it. The warning printed
is the following:

  warning: unable to chain up to private base constructor

Kind Regards
-- 
Mike