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.
Mutex debugging code (used when the ISC_MUTEX_DEBUG preprocessor macro
is set to 1 and PTHREAD_MUTEX_ERRORCHECK is defined) has been broken for
the past 3 years (since commit 2f3eee5a4fdad6606135116c70875b3180c7ed83)
and nobody complained, which is a strong indication that this code is
not being used these days any more. External tools for detecting
locking issues are already wired into various GitLab CI checks. Drop
all code depending on the ISC_MUTEX_DEBUG preprocessor macro being set.
Mutex profiling code (used when the ISC_MUTEX_PROFILE preprocessor macro
is set to 1) has been broken for the past 3 years (since commit
0bed9bfc28a204cde57c6f68170ecc89ebfa6dc8) and nobody complained, which
is a strong indication that this code is not being used these days any
more. External tools for both measuring performance and detecting
locking issues are already wired into various GitLab CI checks. Drop
all code depending on the ISC_MUTEX_PROFILE preprocessor macro being
set.
The Windows support has been completely removed from the source tree
and BIND 9 now no longer supports native compilation on Windows.
We might consider reviewing mingw-w64 port if contributed by external
party, but no development efforts will be put into making BIND 9 compile
and run on Windows again.
