2006-05-14  Michael Natterer  <mitch@gimp.org>

	Allow to initialize a new layer mask with any of the image's
	channels. Fixes bug #310207.

	* libgimpbase/gimpbaseenums.h (enum GimpAddMaskType): added
	value GIMP_ADD_CHANNEL_MASK.

	* libgimpbase/gimpbaseenums.c
	* tools/pdbgen/enums.pl: regenerated.

	* app/core/gimplayer.[ch] (gimp_layer_create_mask): added
	GimpChannel* parameter. Hacked the GIMP_ADD_SELECTION_MASK code a
	bit so it can handle GIMP_ADD_CHANNEL_MASK too. Cleaned up the
	function a bit.

	* app/dialogs/layer-add-mask-dialog.[ch]: added a menu of the
	image's channels.

	* app/actions/layers-commands.c (layers_add_mask_response): pass
	the channel selected in the menu to gimp_layer_create_mask().

	* tools/pdbgen/pdb/layer.pdb (layer_create_mask): use the image's
	active channel when GIMP_ADD_CHANNEL_MASK is passed. Fail if there
	is no active channel.

	* app/pdb/layer_cmds.c: regenerated.