Log Message:
mutt: Update to version 1.13.0

Changes since version 1.12.2:
! <half-up> and <half-down> in the pager are now symmetric.
! $ssl_force_tls is now set by default.
! Configure option --with-regex is renamed to --with-bundled-regex.
  Most modern OS should be fine using their own regex library.  The
  rename is to clarify the intention of the option.
! Configure option --disable-doc now only disables the manual generation.
  Other parts of the doc directory (man pages, Muttrc file) are generated.
! $user_agent is now unset by default.
! unattachments now has a '*' parameter to remove all attachment counting.
+ Autocrypt support.  Enabled via configure option --enable-autocrypt.
  Please see the manual for details on how to enable and use this properly.
+ Byte size displays can be customized via new variables $size_show_bytes,
  $size_show_mb, $size_show_fractions, $size_units_on_left.
+ $ssl_use_tlsv1_3, default set, allows TLS1.3 connections if supported
  by the server.
! format=flowed space stuffing works again, and is performed after every
  edit, not just the first time.
+ $browser_sticky_cursor, default set, attempts to keep the cursor on the
  same mailbox when performing operations in the browser.
! <display-filename> in the browser menu shows the full path for local and
  IMAP mailboxes.
! $sidebar_folder_indent and $sidebar_short_path are now based on previous
  entries in the sidebar, allowing them to work on mailboxes outside $folder.
! Sidebar entries are now prefixed with mailbox shortcuts '~' and '='.  This
  uses the same code as other parts of mutt, for more consistent display.
+ <browse-mailboxes> allows direct access to the mailboxes list from the
  index and pager, without having to use a macro.  This improves
  $browser_sticky_cursor initial selection of the current mailbox.
! <pipe-message> with $pipe_decode set will update MIME headers to decoded
  text/plain values.
+ $send_multipart_alternative and $send_multipart_alternative_filter allow
  the generation of a multipart/alternative when composing a message.  See
  their documentation in the manual for more details.  Also see
  contrib/markdown2html for a sample filter.
+ In the compose menu <view-alt>, <view-alt-text>, \ 
<view-alt-mailcap> allow
  previewing the output of the $send_multipart_alternative_filter.
! $write_bcc now defaults unset.  It no longer affects the Fcc copy, which
  will always include the Bcc header.
+ When $count_alternatives is set, Mutt will recurse inside
  multipart/alternatives while performing attachment searching and counting.
  This affects %X in the index and ~X pattern matching.