if "disable_raw_ctor" is set on the opaque type.
* gtk/Gtk.metadata: Make GtkTargetList opaque (fixes a crash in
Gtk.Drag.Begin), hide the generated constructor and ref/unref
methods, and fix up the interpretation of AddTable.
* gtk/TargetList.custom (TargetList, ~TargetList): Implement the
suppressed constructors and add a finalizer, which handle
refcounting the underlying struct.
(Add, Find, Remove): convenience overloads that take string
instead of Gdk.Atom.
* gtk/Makefile.am (customs): add TargetList.custom
svn path=/trunk/gtk-sharp/; revision=35135
