Issue a deprecation warning if tls-required is used in pop3d or imap4d config
Fix coredump if crypt returns NULL.

* libmailutils/auth/system.c: Check return from crypt before passing it
to strcmp.
* libmu_auth/sql.c: Likewise.
Use global TLS setting in inetd mode (bug #40891)

* imap4d/imap4d.c (imap4d_connection): Use global TLS setting if
no local one was supplied.
(main): Use global TLS setting in inetd mode.
* pop3d/pop3d.c (main): Use global TLS setting in inetd mode.
Update copyright years.
Move biff notification to the library.  Implement it in inc and movemail.

* include/mailutils/mailbox.h (mu_mailbox_set_notify)
(mu_mailbox_unset_notify): New protos.
* include/mailutils/sys/mailbox.h (_mu_mailbox) <notify_user>
<notify_fd,notify_sa>: New members.
* libmailutils/mailbox/Makefile.am (libmailbox_la_SOURCES): Add
biffnotify.c
* libmailutils/mailbox/biffnotify.c: New file.
* libmailutils/mailbox/mailbox.c (_mailbox_create_from_record): Initialize
notify_fd.
(mu_mailbox_destroy): Free notify_sa.
(mu_mailbox_close): Close notify_fd.
(mu_mailbox_flush): Rewrite to handle append-only mailboxes effectively.
* libmailutils/server/msrv.c (server_cfg_param): Fix docstring.
* libmailutils/stream/file_stream.c (fd_open): Open fd read-write if
both MU_STREAM_APPEND and MU_STREAM_READ are requested.
* libproto/mbox/mbox.c (mbox_expunge0): Rescan the mailbox if
messages_count == 0. Special handling for append-only mailboxes.
* maidag/deliver.c: Use library notification mechanism.
* mh/inc.c: New option --notify.
* movemail/movemail.c: Likewise.
Accept single-dash notify option to inc

* mh/mh_getopt.c (mh_getopt): Correctly handle traditional options
that begin with "no" (e.g. "notify").
* mh/inc.c (mh_option): Accept -notify (single-dash).