* dired.el (dired-mode-map): Rebind "\C-t\C-t" from
`image-dired-dired-insert-marked-thumbs' to
`image-dired-dired-toggle-marked-thumbs'.
* image-dired.el: Require cl when compiling.
(image-dired-dired-toggle-marked-thumbs): Rename from
`image-dired-dired-insert-marked-thumbs'. Add ARG. Doc fix.
Use interactive spec "P". Set LOCALP arg of `dired-get-filename'
to 'no-dir. Skip files whose names don't match
`image-file-name-regexp'. When file has a thumbnail overlay,
delete it. (Bug#5270)