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

	* app/core/gimpimage.[ch]: added "gboolean alpha_changed" to
	GimpImageFlushAccumulator. Install an "alpha_changed" handler
	on gimage->layers and set flush_accum.alpha_changed = TRUE
	whenever the image's *only* layer changed its alpha.

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