This commit converts the license handling to adhere to the REUSE
specification. It specifically:
1. Adds used licnses to LICENSES/ directory
2. Add "isc" template for adding the copyright boilerplate
3. Changes all source files to include copyright and SPDX license
header, this includes all the C sources, documentation, zone files,
configuration files. There are notes in the doc/dev/copyrights file
on how to add correct headers to the new files.
4. Handle the rest that can't be modified via .reuse/dep5 file. The
binary (or otherwise unmodifiable) files could have license places
next to them in <foo>.license file, but this would lead to cluttered
repository and most of the files handled in the .reuse/dep5 file are
system test files.
3882. [func] By default, negative trust anchors will be tested
periodically to see whether data below them can be
validated, and if so, they will be allowed to
expire early. The "rndc nta -force" option
overrides this behvaior. The default NTA lifetime
and the recheck frequency can be configured by the
"nta-lifetime" and "nta-recheck" options. [RT #36146]
