Replace thread_policy with C++11 threads support #7
Description
There is already a PR which adds C++11 thread support as a separate thread_policy: SoundScapeRenderer/ssr#57.
However, since threads are now supported natively in C++, the whole concept of a thread_policy isn't necessary anymore.
It should be removed and replaced by using native threads.
The only question is: should there be a build flag to allow compilation with a compiler that doesn't support native C++ threads?
Since we are already using C++11 features in many places, I guess this really shouldn't be necessary.