Eevee: Add support for new Hair geometry system.

This now can shade actual poly strips that mimics cylinders.
This makes hair coverage exact compared to the line method and result in
smoother fading hair.

This does make the sampling a bit more exact but needs more samples to
converge properly.

source/blender/draw/engines/eevee/eevee_engine.c

@@ -190,6 +190,10 @@ static void eevee_draw_background(void *vedata)
 	/* Default framebuffer and texture */
 	DefaultTextureList *dtxl = DRW_viewport_texture_list_get();
 	DefaultFramebufferList *dfbl = DRW_viewport_framebuffer_list_get();
+
+	/* Refresh Hair */
+	DRW_draw_pass(psl->hair_tf_pass);
+
 	/* Sort transparents before the loop. */
 	DRW_pass_sort_shgroup_z(psl->transparent_pass);