2004-03-15  Michael Natterer  <mitch@gimp.org>

	* app/core/gimpdrawable.c (gimp_drawable_real_set_tiles): emit
	"alpha_changed" if the drawable got/lost an alpha channel by
	setting the new tiles.

	* app/core/gimpimage-undo-push.c (undo_pop_layer_mod)
	* app/core/gimplayer.c (gimp_layer_add_alpha): removed explicit
	calls to gimp_drawable_alpha_changed().