2002-06-16  Hans Breuer  <hans@breuer.org>

	* lib/plug-in.[hc] : make PlugInInfo opaque again in the
	good tradition of information hiding. Add new function
	dia_plugin_get_symbol()
	* app/sheets.c app/sheets_dialog_callbacks.c : use it

	* app/sheets.c : stop complaining about object_get_type()
	returning NULL. This is a consequence of e.g. disabling
	plug-ins at runtime _and_ it was and is gracefully handled.
	Spitting out g_warning for it isn't appropriate.

	* lib/object.[ch] : removed dead code

	* app/plugin-mangager.c : almost complete rewrite for gtk2
	using GtkListStore/GtkTreeView

	* lib/libdia.def : updated externals

	* todo.gtk2 : updated, that is removed already done steps