screen: Update to 4.9.0

screen: Update to 4.9.0

Full changelog as per https://savannah.gnu.org/forum/forum.php?forum_id=10107:

New in this release:
  * Hardstatus option for used encoding (escape string '%e')
  * OpenBSD uses native openpty() from its utils.h
  * Fixes:
    - fix combining char handling that could lead to a segfault
    - CVE-2021-26937: possible denial of service via a crafted UTF-8 character sequence (bug #60030)
    - make screen exit code be 0 when checking --help
    - session names limit is 80 symbols (bug #61534)
    - option -X ignores specified user in multiuser env (bug #37437)
    - a lot of reformations/fixes/cleanups (man page and source code)

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Reviewed-by: Adolf Belka <adolf.belka@ipfire.org>