The following new commands have been added:

DIRECTORY-MODE-MARK-DIRECTORIES

Mark all directories in the current buffer except '..'.
With prefix argument ARG, unmark all those directories.

DIRECTORY-MODE-MARK-LINKS

Mark all symbolic links in the current buffer.
With prefix argument ARG, unmark all those links.

DIRECTORY-MODE-MARK-SUFFIX

Mark all files with the given SUFFIX.
The provided SUFFIX is a string, and not a file extenion, meaning every file with
a name ending in SUFFIX will be marked.
With prefix argument ARG, unmark all those files.

DIRECTORY-MODE-MARK-EXTENSION

Mark all files with the given EXTENSION.
A '.' is prepended to the EXTENSION if not present.
With prefix argument ARG, unmark all those files.

DIRECTORY-MODE-NEXT-MARK

Move to the next Nth marked entry.

DIRECTORY-MODE-PREVIOUS-MARK

Move to the previous Nth marked entry.

The DIRECTORY-MODE-MARK-REGEXP command has an additional prefix argument to behave like the other commands.