2003-08-25  Sven Neumann  <sven@gimp.org>

	Fixed some issues with the PDB thumbnail functions spotted by
	Wolfgang Hofer and loosely based on patches he provided:

	* tools/pdbgen/pdb/fileops.pdb (file_load_thumbnail): keep a
	reference on the GimpImagefile as long as we need the associated
	preview temp_buf. Call gimp_imagefile_update() before requesting
	the preview.

	* app/pdb/fileops_cmds.c: regenerated.

	* app/base/temp-buf.c (temp_buf_new_check): use a checkerboard
	algorithm similar to the one the displayshell-render code uses.