2004-03-14  Simon Budig  <simon@gimp.org>

	* app/core/gimpimage.[ch]
	* app/core/gimpimage-undo.c: introduced a freeze counter, so
	that undo_freeze(); undo_freeze(); undo_thaw(); no longer
	results in an thawed undo stack.

	Fixes Bug #124176.

	This might reveal other places in the code where
	gimp_image_undo_freeze/thaw or gimp_image_undo_disable/enable
	were used in an inconsistent (not-paired) manner.

	* app/file/file-open.c: e.g. here, where _enable was called on
	the new image. The intention was to free a potential undo stack,
	so now call gimp_image_undo_free() instead.