GL_ARB_sample_shading
http://www.opengl.org/registry/specs/gl/ARB/sample_shading.txt
GL_ARB_sample_shading
	GL_SAMPLE_SHADING_ARB 0x8C36
	GL_MIN_SAMPLE_SHADING_VALUE_ARB 0x8C37
	void glMinSampleShadingARB (GLclampf value)