package/bind: security bump to version 9.11.19

Fixes the following security issues:

- (9.11.18) DNS rebinding protection was ineffective when BIND 9 is
  configured as a forwarding DNS server.  Found and responsibly reported by
  Tobias Klein.  [GL #1574]

- (9.11.19) To prevent exhaustion of server resources by a maliciously
  configured domain, the number of recursive queries that can be triggered
  by a request before aborting recursion has been further limited.  Root and
  top-level domain servers are no longer exempt from the
  max-recursion-queries limit.  Fetches for missing name server address
  records are limited to 4 for any domain.  This issue was disclosed in
  CVE-2020-8616.  [GL #1388]

- (9.11.19) Replaying a TSIG BADTIME response as a request could trigger an
  assertion failure.  This was disclosed in CVE-2020-8617.  [GL #1703]

Also update the COPYRIGHT hash for a change of copyright year and adjust the
spacing for the new agreements.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>