GL_SGIX_fog_layers
http://www.opengl.org/registry/specs/SGIX/fog_layers.txt
GL_SGIX_fog_layers

	GL_FOG_TYPE_SGIX 0x8323
	GL_UNIFORM_SGIX 0x8324
	GL_LAYERED_SGIX 0x8325
	GL_FOG_GROUND_PLANE_SGIX 0x8326
	GL_FOG_LAYERS_POINTS_SGIX 0x8327
	GL_MAX_FOG_LAYERS_POINTS_SGIX 0x8328
	void glFogLayersSGIX (GLsizei n, const GLfloat* points)
	void glGetFogLayersSGIX (GLfloat* points)
