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.
- when transfer-source(-v6), query-source(-v6), notify-source(-v6)
or parental-source(-v6) are specified with a port number, issue a
warning.
- when the port specified is the same as the DNS listener port (i.e.,
53, or whatever was specified as "port" in "options"), issue a fatal
error.
- check that "port" is in range. (previously this was only checked
by named, not by named-checkconf.)
- added checkconf tests.
- incidental fix: removed dead code in check.c:bind9_check_namedconf().
(note: if the DNS port is specified on the command line with "named -p",
that is not conveyed to libbind9, so these checks will not take it into
account.)
