GitLab

(thumbs-thumbsdir): Force `thumbs-thumbsdir' to be interpretable as a directory.
(thumbs-thumbname): Remove directory separator from format string;
`thumbs-thumbsdir' now returns a valid directory name.
(thumbs-temp-dir): New defsubst.
(thumbs-temp-file, thumbs-resize-image, thumbs-modify-image): Use it.