changed thumbnailing to not draw the frame into the
	thumbnail images themselves anymore; instead, draw it at the time
	they're loaded. This makes anti-aliased thumbnail variants no
	longer necessary, so they're no longer used.  There's a cheap test so
	old thumbnails aren't framed twice.

	* libnautilus-private/nautilus-thumbnails.c: (make_thumbnail_uri),
	(make_thumbnails), (pixel_matches_value), (pixbuf_is_framed),
	(nautilus_thumbnail_load_framed_image):
	don't frame the thumbnails at creation time; instead, provide
	a routine to frame them at load time if necessary.

	* libnautilus-private/nautilus-thumbnails.h:
	added nautilus_thumbnail_load_framed_image

	* libnautilus-private/nautilus-icon-factory-private.h:
	added nautilus_icon_factory_get_thumbnail_frame

	* libnautilus-private/nautilus-icon-factory.c:
	(load_thumbnail_frames), (nautilus_icon_factory_initialize),
	(nautilus_icon_factory_destroy), (icon_theme_changed_callback),
	(load_icon_from_path), (load_named_icon), (load_specific_icon),
	(nautilus_icon_factory_get_thumbnail_frame):
	made it call nautilus_thumbnail_load_framed_image to load
	thumbnails; made the icon factory load the thumbnail frames so it
	doesn't have to be done repeatedly; changed how the aa flag is
	passed around a little, although this could be cleaned up more now.