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 isc_queue_new() was using dirty tricks to allocate the head and tail
members of the struct aligned to the cacheline. We can now use
isc_mem_get_aligned() to allocate the structure to the cacheline
directly.
Use ISC_OS_CACHELINE_SIZE (64) instead of arbitrary ALIGNMENT (128), one
cacheline size is enough to prevent false sharing.
Cleanup the unused max_threads variable - there was actually no limit on
the maximum number of threads. This was changed a while ago.
