The repository now contains a clang-format file which should be used when committing new code. Additionally, a new workflow job is added which checks the conformance of source files to the specified formatting rules.
Fixes#47.
TerminatableThread is now implemented by using std::thread. The terminate()
function provided by the base class was actually not used anywhere, and was
removed along with the base class itself.
As a bonus, the completely unused files common_win32.{cpp,h} are also removed.