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.
The fuzzing tests were temporarily disabled when the build system has been
converted to automake. This commit restores the functionality to run the
fuzzing tests as part of the `make check`. When the afl or libfuzzer
is enabled via ./configure, it uses a custom LOG_DRIVER (fuzz/<fuzzer.sh>).
Currently only libfuzzer.sh has been implemented that runs each fuzz
test for 5 seconds each.
