Mesa's LLVMpipe + Lavapipe Land FP16 Support

The latest work landing for Mesa 21.3 is supporting FP16 within the LLVM-based software driver code namely for the LLVMpipe Gallium3D OpenGL and Lavapipe Vulkan drivers.

VK_KHR_shader_float16_int8 and VK_KHR_shader_subgroup_extended_types are now exposed for the LLVMpipe code with this OpenGL FP16 support in place. The Lavapipe Vulkan code is similarly exposing this FP16 support too.

Those having interest in FP16 support for these drivers can find out more via this merge request.

Separately, the Mesa 21.3 release schedule is now firmed up with plans of branching and first release candidate on/around 13 October, weekly release candidates as usual, and hoping to release Mesa 21.3 by mid-November. As with most Mesa quarterly releases, there is a lot in store for performance optimizations, new hardware support, and new OpenGL/Vulkan driver features.