WaitfreeQueue: Add PPoPP'12 version.

Source:

A. Kogan and E. Petrank. A methodology for creating fast wait-free data
structures. In Proceedings of the 17th ACM SIGPLAN symposium on Principles and
Practice of Parallel Programming, PPoPP ’12, pages 141–150, New York, NY, USA,
2012. ACM.

Signed-off-by: Michael Lippautz <michael.lippautz@gmail.com>