bug#18009: 24.4.50; Add hooks for `rename-file' and `delete-file'

[Drew Adams]

> One use case: Bookmark+ autofile bookmarks have the same name as their
> files.  (There can be multiple bookmarks with the same name,
> corresponding to files with the same name in different directories.)
> With a hook it would be trivial to automatically rename or delete the
> associated bookmark.

Besides that use case, which is specific to Bookmark+, it could be
useful to (optionally) automatically relocate any (i.e. vanilla)
bookmarks whose files were renamed.  Currently, such relocation is
entirely manual (command `bookmark-relocate').