* Kill the thread only if is alive.
* Remove rz_th_lock_guard.
* Use rz_sys_usleep since pthread_yield/sched_yield are not portable.
* Kill threads only on error.
* Avoid killing already-dead threads.
* RzThreadFunction now returns void* and added test_thread_queue.
* Removed pthread_exit
* Create `rz_windows.h`
* Move `RzThread` structure definitions to internal header
* Create and use `rz_th_get_user()` API to avoid exposing `RzThread` layout in external header
* Make `rz_th_self()` an IPI
* Use `_wmkdir()` in `rz_sys_mkdir()` on Windows
* Remove unused `winkd_break_read` function
* Remove `RzIORap` definition from `rz_io.h`
* Remove include of `Windows.h` from `rz_types.h`
* Use `rz_windows.h` when necessary
* Remove `RzCoreRtrHost` definition from `rz_core.h`
* Remove `rz_socket.h` include from `rz_core.h`
