Native bindings to the NV_path_rendering_shared_edge extension.

This extension introduces a new path command modifier to the NV_path_rendering extension to indicate that a path command represents an edge (either straight or curved) that is shared with another path.

When used in conjunction with NV_framebuffer_mixed_samples, a shared edge (or a whole path including shared edges) will use modified rasterization rules in order to ensure that groups of raster samples associated with a given coverage sample will all produce consistent coverage results, in order to avoid artifacts described further in the issues section at the end of this document.

Requires NV_path_rendering.