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.
Test for Ed25519 and Ed448. If both algorithms are not supported, skip
test. If only one algorithm is supported, run test, skip the
unsupported algorithm. If both are supported, run test normally.
Create new ns3. This will test Ed448 specifically, while now ns2 only
tests Ed25519. This moves some files from ns2/ to ns3/.
