gail: use connect_object() for connecting to GtkTextBuffer signals
gail: use connect_object() for connecting to GtkTextBuffer signals

because the user_data is the GtkTextView. This used to crash when the
text view got destroyed, and the buffer was used for another view.
Fixes bug #652204.

johne53/MB3Gtk-2,johne53/MB3Gtk-2,Distrotech/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2