Publish Intel SPIR-V Extensions

[bashbaug]

This change adds the following extensions:

• cl_intel_spirv_subgroups
• cl_intel_spirv_media_block_io
• cl_intel_spirv_device_side_avc_motion_estimation

These extensions extend the SPIR-V environment to consume modules using the SPIR-V extensions SPV_INTEL_subgroups, SPV_INTEL_media_block_io, and SPV_INTEL_device_side_avc_motion_estimation.

Additionally, this change:

• Fixes a few typos, formatting errors, and bugs in the cl_intel_device_side_avc_motion_estimation extension.
• Converts the cl_intel_subgroups, cl_intel_subgroups_short, and cl_intel_required_subgroup_size extensions from plain text to HTML.