main/bind: security upgrade to 9.16.6
Fixes CVEs:
- CVE-2020-8620: A specially crafted large TCP payload can trigger an assertion failure in tcpdns.c
- CVE-2020-8621: Attempting QNAME minimization after forwarding can lead to an assertion failure in resolver.c.
- CVE-2020-8622: A truncated TSIG response can lead to an assertion failure.
- CVE-2020-8623: A flaw in native PKCS#11 code can lead to a remotely triggerable assertion failure in pk11.c.
- CVE-2020-8624: update-policy rules of type "subdomain" are enforced incorrectly