Native bindings to the INTEL_conservative_rasterization extension.

Regular rasterization includes fragments with at least one sample covered by a polygon. Conservative rasterization includes all fragments that are at least partially covered by the polygon.

In some use cases, it is also important to know if a fragment is fully covered by a polygon, i.e. if all parts of the fragment are within the polygon. An application may, for example, want to process fully covered fragments different from the "edge" pixels. This extension adds an option for the fragment shader to receive this information via gl_SampleMaskIn[].