Using FindOpenCL.cmake module from vexcl project.  I changed the
variables to agree with the variable names used in boost.compute:
OPENCL_INCLUDE_DIRS->OpenCL_INCLUDE_DIRS
OPENCL_LIBRARIES->OpenCL_LIBRARY
Merge branch 'master' of https://github.com/d-meiser/compute

Conflicts:
	cmake/FindOpenCL.cmake