2004-02-27  Rob Adams  <readams@readams.net>

	Handle layer promotion of transient descendants of layer-promoted
	windows to also be layer promoted, using a simple iterative
	algorithm.

	* src/stack.c (compute_layer): change name to promote_layer, and
	convert to simply perform any necessary layer promotion without
	computing the standalone layer.
	(max_layer_func): use window->layer instead of
	get_standalone_layer
	(get_maximum_layer_of_ancestor): use window->layer instead of
	get_standalone_layer
	(meta_stack_ensure_sorted): implement iterative algorithm,
	explained in a long comment.

	* src/window.h: add a tmp_layer field used by stack.c for
	determining if the stack is dirty or not, since maintaining this
	information in meta_stack_ensure_sorted is no longer practical.