OpenCL 3.0 Reference Pages

This issue is to track tasks and progress to update the OpenCL reference pages for OpenCL 3.0.

Task list (will grow):

* [ ] Update any of the static pages (including the main index page) from OpenCL 2.2 to 3.0.
* [x] Update the reference page links from the 2.2 specs to the 3.0 specs (mostly a script change?).
* [x] At least add stub pages for the missing links to fix the 404 errors, assuming the we can't refactor the spec to easily generate them.
* [ ] At least add stub pages for any new extensions (list TBD).
* [ ] Perhaps add pages for any new OpenCL 3.0 concepts (e.g. OpenCL C features, list TBD).

Some related issues (mostly for the 2.2 reference pages):

* https://github.com/KhronosGroup/OpenCL-Docs/issues/70
* https://github.com/KhronosGroup/OpenCL-Docs/issues/246
* https://github.com/KhronosGroup/OpenCL-Registry/issues/94

Start with the OpenCL reference pages, static pages including the main index, and the script mentioned for reference links; review the related issues for prior 2.2 work. Done means updating remaining 2.2 references to 3.0, adding stubs for new extensions and missing concepts, and completing the checklist as its scope becomes defined.

Written by the indexing model from the issue text.