Log Message:
neomutt: update to 20211015.

* Security
  - Fix CVE-2021-32055
* Features
  - threads: implement the `$use_threads` feature
    https://neomutt.org/feature/use-threads
  - hooks: allow a -noregex param to folder and mbox hooks
  - mailing lists: implement list-(un)subscribe using RFC2369 headers
  - mailcap: implement x-neomutt-nowrap flag
  - pager: add `$local_date_header` option
  - imap, smtp: add support for authenticating using XOAUTH2
  - Allow `<sync-mailbox`> to fail quietly
  - imap: speed up server-side searches
  - pager: improve skip-quoted and skip-headers
  - notmuch: open database with user's configuration
  - notmuch: implement `<vfolder-window-reset>`
  - config: allow += modification of my_ variables
  - notmuch: tolerate file renames behind neomutt's back
  - pager: implement `$pager_read_delay`
  - notmuch: validate `nm_query_window_timebase`
  - notmuch: make $nm_record work in non-notmuch mailboxes
  - compose: add `$greeting` - a welcome message on top of emails
  - notmuch: show additional mail in query windows
* Changed Config
- Renamed lots of config, e.g.  `askbcc` to `ask_bcc`.
* Bug Fixes
  - imap: fix crash on external IMAP events
  - notmuch: handle missing libnotmuch version bumps
  - imap: add sanity check for qresync
  - notmuch: allow windows with 0 duration
  - index: fix index selection on `<collapse-all>`
  - imap: fix crash when sync'ing labels
  - search: fix searching by Message-Id in `<mark-message>`
  - threads: fix double sorting of threads
  - stats: don't check mailbox stats unless told
  - alias: fix crash on empty query
  - pager: honor mid-message config changes
  - mailbox: don't propagate read-only state across reopens
  - hcache: fix caching new labels in the header cache
  - crypto: set invalidity flags for gpgme/smime keys
  - notmuch: fix parsing of multiple `type=`
  - notmuch: validate $nm_default_url
  - messages: avoid unnecessary opening of messages
  - imap: fix seqset iterator when it ends in a comma
  - build: refuse to build without pcre2 when pcre2 is linked in ncurses
* Translation updates