Expose cl::Buffer in backend::opencl::device_vector
Expose cl::Buffer in backend::opencl::device_vector

See #98

Poulpy21/vexcl,Poulpy21/vexcl,Poulpy21/vexcl,kapadia/vexcl,ddemidov/vexcl,kapadia/vexcl,ddemidov/vexcl