Pheet meets C++11

Pheet is a C++ task-scheduling framework that allows for easy customization of internal data-structures. The implementation was started before the C++11 standard was committed and therefore did not use the new standardized memory model but compiler/platform specific intrinsics for atomic memory operations. This not only makes the implementation harder to port to other compilers or architectures but also suffers from the fact that prior C++ versions did not specify any memory model. In this report I discuss the porting of one of the internal Pheet data structures to the new memory model and provide reasoning about the correctness based on the semantics of the memory consistency model. Using two benchmarks from the Pheet benchmark suite I compare the performance of the original against the new implementation which shows a significant speedup under certain conditions on one of the two test machines.