Add double buffering

[timuraudio]

Add a class template double_buffered_object implementing the double buffering technique described in Dave Rowland and Fabian Renn-Giles talk "Realtime 101" (from 22:50): https://www.youtube.com/watch?v=ndeN983j_GQ&t=1370s

[nicolasdanet]

Have you ever seen the < https://www.youtube.com/watch?v=j2AgjFSFgRc > Matthias Killat talk?
It might be related.

[timuraudio]

No, I haven't! Thanks, I will definitely check it out!