swr/rasterizer: Add tessellator implementation to the rasterizer

swr/rasterizer: Add tessellator implementation to the rasterizer

This is initial commit on the way to implement ARB_tessellation_shader
extension in OpenSWR. It introduces tessellator implementation
taken from Microsoft GitHub (published under MIT license):

https://github.com/microsoft/DirectX-Specs/blob/master/d3d/archive/images/d3d11/tessellator.cpp
https://github.com/microsoft/DirectX-Specs/blob/master/d3d/archive/images/d3d11/tessellator.hpp

It also adds some glue code that connects the tessellator
to the internals of SWR rasterizer.

Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Bruce Cherniak <bruce.cherniak@intel.com>
Reviwed-by: Alok Hota <alok.hota@intel.com>