TODOs

- *_from_int_ptr, register with metaclass
- generic_info
- Incorporate fixes in C++ stuff from after the fork
- compare and tests
- MemoryPool
- enqueue_nd_range_kernel size/offset mess

- CommandQueue.set_property
- GLBuffer
- GLRenderBuffer
- GLTexture
- get_gl_context_info_khr
- ?clEnqueueNativeKernel

- Buffer interface functions should really use new-style buffer interface
  (old-style does not work in Py3)
  https://github.com/numpy/numpy/issues/4747