bind: Update to 9.16.50

bind: Update to 9.16.50

For details see:
https://downloads.isc.org/isc/bind9/9.16.50/doc/arm/html/notes.html#notes-for-bind-9-16-50

"New Features

Added RESOLVER.ARPA to the built in empty zones."

Important:
"This is the last maintenance release of BIND 9.16. This version is now end of life. Please upgrade to
BIND 9.18, the current stable version."

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>