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.
Add a simple stats unit test that tests the existing library functions
isc_stats_ncounters, isc_stats_increment, isc_stats_decrement,
isc_stats_set, and isc_stats_update_if_greater.
We should drop the HISTORY file because it's confusing and the same
information is covered by the release notes for .0 releases (or at
least they should be).
Remove references to the HISTORY file, update the README to tell
people go look somewhere else.
This was written down in the outdated doc/dev/release documentation.
Since the rest of that file can go, add these steps to a separate file
and update it to current standards (e.g. use git commands).
