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 system tests were missing a test that would test tcp-initial-timeout
and tcp-idle-timeout.
This commit adds new "timeouts" system test that adds:
* Test that waits longer than tcp-initial-timeout and then checks
whether the socket was closed
* Test that sends and receives DNS message then waits longer than
tcp-initial-timeout but shorter time than tcp-idle-timeout than
sends DNS message again than waits longer than tcp-idle-timeout
and checks whether the socket was closed
* Similar test, but bursting 25 DNS messages than waiting longer than
tcp-initial-timeout and shorter than tcp-idle-timeout than do second
25 DNS message burst
* Check whether transfer longer than tcp-initial-timeout succeeds
