[RFC] Interop between OpenCL and OpenGL

Adds the API functionality from OpenCl 1.0 for interop between OpenGL and OpenCL.

Now resides at JuliaGPU/OpenCL.jl/opengl

- [ ] add tests
- [ ] Implement OCL 1.1 functions like http://www.khronos.org/registry/cl/sdk/1.1/docs/man/xhtml/clGetGLContextInfoKHR.html