Minor cleanup and simplification.

Minor cleanup and simplification.
* filecache.el (file-cache-add-directory, file-cache-add-directory-recursively)
(file-cache-add-from-file-cache-buffer)
(file-cache-delete-file-regexp, file-cache-delete-directory)
(file-cache-files-matching-internal, file-cache-display): Use dolist.
(file-cache-temp-minibuffer-message): Delete function.
(file-cache-minibuffer-complete): Use minibuffer-message instead.