This adds third-party performance tests to use in comparing
Boost.Compute with other parallel/GPGPU frameworks like Intel's
TBB and NVIDIA's Thrust along with the C++ STL.
Also refactors the timing and profiling infrastructure and adds
a simple perf.py driver script for running performance tests.
This adds interoperability support between Boost.Compute and various
other C/C++ libraries (Eigen, OpenCV, OpenGL, Qt and VTK). This eases
development for users using external libraries with Boost.Compute.