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.
- managed-keys is now deprecated as well as trusted-keys, though
it continues to work as a synonym for dnssec-keys
- references to managed-keys have been updated throughout the code.
- tests have been updated to use dnssec-keys format
- also the trusted-keys entries have been removed from the generated
bind.keys.h file and are no longer generated by bindkeys.pl.
- any use of trusted or static keys for the root zone will now
elicit a warning, regardless of what the keys may be
- ditto for any use of a key for dlv.isc.org, static or managed
