Major internal restructuring for the GTK GUI,

GObject-derived wrappers are used for tr_handle_t and tr_torrent_t.
Use bencoding to store prefs and state file.
Make sure to always group error messages when adding multiple torrents at once.
Remove some unused code.
Many miscellaneous cleanups.

gtk/tr_backend.h

@@ -0,0 +1,56 @@
+#ifndef TR_BACKEND_H
+#define TR_BACKEND_H
+
+#include <glib-object.h>
+
+#include "transmission.h"
+#include "bencode.h"
+
+#define TR_BACKEND_TYPE		  (tr_backend_get_type ())
+#define TR_BACKEND(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST ((obj), TR_BACKEND_TYPE, TrBackend))
+#define TR_BACKEND_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_CAST ((klass), TR_BACKEND_TYPE, TrBackendClass))
+#define TR_IS_BACKEND(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE ((obj), TR_BACKEND_TYPE))
+#define TR_IS_BACKEND_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_TYPE ((klass), TR_BACKEND_TYPE))
+#define TR_BACKEND_GET_CLASS(obj) \
+  (G_TYPE_INSTANCE_GET_CLASS ((obj), TR_BACKEND_TYPE, TrBackendClass))
+
+typedef struct _TrBackend TrBackend;
+typedef struct _TrBackendClass TrBackendClass;
+
+/* treat the contents of this structure as private */
+struct _TrBackend {
+  GObject parent;
+  tr_handle_t *handle;
+  GList *torrents;
+  gboolean disposed;
+};
+
+struct _TrBackendClass {
+  GObjectClass parent;
+};
+
+GType
+tr_backend_get_type(void);
+
+TrBackend *
+tr_backend_new(void);
+
+tr_handle_t *
+tr_backend_handle(TrBackend *back);
+
+void
+tr_backend_save_state(TrBackend *back, char **errstr);
+
+GList *
+tr_backend_load_state(TrBackend *back, benc_val_t *state, GList **errors);
+
+#ifdef TR_WANT_BACKEND_PRIVATE
+void
+tr_backend_add_torrent(TrBackend *back, GObject *tor);
+#endif
+
+#endif