* lisp/image/image-dired.el (image-dired-delete-marked): Remove command,
because it was too buggy.
(image-dired-do-flagged-delete): New command that does almost the same
as the above removed command but with flagged images.
(image-dired-thumbnail-mode-map): Bind "x" to
'image-dired-do-flagged-delete'.