Add files for the attachment_filters setting.
Indicate that attachment alteration rules must be moved to the
attachment_filters setting.
Move the rules that alter or remove parts to the attachment_filters
configuration setting.
The attachment_filters setting is part of the "deliver" category, but the
attachment_rules setting is not.
attachment_rules -> attachment_filters
Mention the attachment_filters setting.
Mention the attachment_filters setting, and add references.
Add a reference to the attachment_filters setting.
List the attachment_filters help file.
(parse_attachment_filters)  New routine.
  Parse the attachment_filters configuration setting.
(_post)  Use the attachment_filters setting to determine how
  messages should be altered.
Add support for the attachment_filters configuration setting.
(_r_strip_body)  Do not allow multipart subparts to be discarded wholesale.
  Bugfix:  call make_singlepart after the subparts have been processed.
  Thanks to Roger Klorese.
(parse_part)  Bugfix:  account for hyphenated interface names in
  command validity tests.  Thanks to Marc Fournier.
(str_to_offset)  Return immediately if no argument is present.
(_unsubscribe)  Bugfix:  do not close the farewell filehandle;
  substitute_vars already does that.
Correct a typo.
Document the new numbered_name and subject_name formats.
Document the new "sort" and "index" fields, which allow the
messages to be sorted, and the index format to be different
for different digests.
Indicate that the archive-sync command can change the dates
in the message database.