merge: upstream fixes

 * crypt-gpgme: prevent crash on bad S/MIME signature
 * Void passphrase on s/mime decryption error
 * smime_handle_entity() cleanup
 * Mention $pgp_decode_command for $pgp_check_gpg_decrypt_status_fd
 * Minor documentation fix
 * Display matching new messages in a thread-limited index
 * Bug fix: reset ctx->vsize in update_index_unthreaded on reopened mailbox
 * Improved limit-to-all detection by skipping leading spaces of the pattern
 * Add ctx->vsize = 0 in a couple of places
 * Handle reopen/new_mail when closing mailbox in <imap-logout-all>
 * Skip sort in mbox_sync_mailbox() when new/reopen occurs
 * Add mx_ops.msg_padding_size to return the padding for a mx type
 * Add message padding to ctx->vsize computation
 * Fix AUXSORT usage in compare_spam
 * Fix -z and -Z options to work with IMAP
 * Create mutt_buffer_increase_size() function
 * Always check UID vs MSN when handling FETCH
 * Refactor out mutt_is_quote_line()
 * Don't match $abort_noattach_regexp on quoted lines
 * Remove legacy trim_incomplete_mbyte() in the pager
 * Remove compare_stat() call in safe_rename()
 * Display an error message if syncing fails
 * Change $query_format to use mutt_format_s
 * Fix alias documentation examples
 * Add additional error handling to safe_rename()
 * Remove extra lstats() in safe_rename() upon link success
 * Add compose-to-sender functionality.