Wed Jun 23 23:52:54 BST 1999 Andy Thomas <alt@gimp.org>

	* gimp/app/gimppreviewcache.c
	* gimp/app/gimppreviewcache.h
	* gimp/app/drawable_cmds.c
	* gimp/app/gdisplay.c
	* gimp/app/gimpdrawableP.h
	* gimp/app/gimage_cmds.c
	* gimp/app/Makefile.am
	* gimp/app/layers_dialog.c
	* gimp/app/channel.c
	* gimp/app/lc_dialog.c
	* gimp/app/lc_dialog.h
	* gimp/app/lc_dialogP.h
	* gimp/app/layer.c
	* gimp/app/gimpdrawable.c
	* gimp/app/internal_procs.c
	* gimp/libgimp/gimp.h
	* gimp/libgimp/gimpimage.c
	* gimp/libgimp/gimpdrawable.c
	* gimp/libgimp/gimpmenu.c
	* gimp/tools/pdbgen/pdb/drawable.pdb
	* gimp/tools/pdbgen/pdb/gimage.pdb

	Added thumbnail image preview functions.
	Previews are visible on the L&C&P dialogs as well as in the
	drawables/channels/ menus generated for plugins
	(see the bumpmap & Mapobject plugins).

	PDB interface exists to simply extract a thumbnail preview
	of a given size. This is much quicker & more efficient
	than getting the image data tile-by-tile if you only need a small
	image since a "preview cache" has been implemented. This cache also
	reduces the number of times the tiles cached is scanned since smaller
	previews are always generated from large ones if they exists and
	are valid.

	Some possible usages (I don't intend to implement these ideas. Just
	suggestions). More plugins using the thumbnail preview (ie any that
	use multiple images). Indication of "active image" somewhere.....
	Actually almost anywhere a drawable/image name appears.