package/screen: add security fix for CVE-2021-26937

package/screen: add security fix for CVE-2021-26937

encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a
denial of service (invalid write access and application crash) or possibly
have unspecified other impact via a crafted UTF-8 character sequence.

For more details, see the oss-security discussion:
https://www.openwall.com/lists/oss-security/2021/02/09/3

So far no fix has been added to upstream git, and a number of early proposed
fixes caused regressions, so pull the security fix from the screen 4.8.0-5
Debian package.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>