Add provisional command-buffer extension (#182)
Add provisional command-buffer extension (#182)

* Add provisional command-buffer extension

Run `gen_headers.py` from https://github.com/KhronosGroup/OpenCL-Headers/pull/161 on XML file
containing https://github.com/KhronosGroup/OpenCL-Docs/pull/711 new spec extensions.

The only XML changes are for the `cl_khr_command_buffer` extension, which declarations gets
generated at the top of `cl_ext.h` by the script. So I have taken the generated
`cl_khr_command_buffer` code and applied it to the same location in master branch `cl_ext.h`.

* Remove INFO from command-buffer query enums

Updated to reflect
https://github.com/KhronosGroup/OpenCL-Docs/pull/711/commits/929586586711de05bd45c05840c3b3d147d4e949

* Reflect command-buffer property changes

1. Change type of `cl_command_buffer_properties_khr` to `cl_properties`
2. Add a new `cl_command_buffer_flags_khr` type.
3. Rename `CL_COMMAND_BUFFER_PROPERTIES_KHR` to
`CL_COMMAND_BUFFER_FLAGS_KHR`.
  3a. Change the expected type of this to `cl_command_buffer_flags_khr`.
4. Change type of `cl_ndrange_kernel_command_properties_khr` to
`cl_properties`
KhronosGroup/OpenCL-Headers,KhronosGroup/OpenCL-Headers