Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

The last big commit: let usr.sbin/ use WARNS=6 by default.

Update BIND to version 9.6.1rc1. This version has better performance and
lots of new features compared to 9.4.x, including:

Full NSEC3 support
Automatic zone re-signing
New update-policy methods tcp-self and 6to4-self
DHCID support.
More detailed statistics counters including those supported in BIND 8.
Faster ACL processing.
Efficient LRU cache-cleaning mechanism.
NSID support.