- Fix wrong version number returned by ibzip2 --version.
 - Use the number of cores the process has affinity for as default parallelism.
 - Write verbose output enabled with the -v option to stderr instead of stdout.
 - Allow decompressing to /dev/null with ibzip2 for benchmarking purposes.
 - Add --oss-attributions to ibzip2.
 - Quit when SIGINT has been sent when called from Python.
 - Spawn threads only when needed instead of all at once at startup.
 - Avoid std::regex initialization during dlopen.