GL_EXT_polygon_offset_clamp
https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_polygon_offset_clamp.txt
GL_EXT_polygon_offset_clamp

	GL_POLYGON_OFFSET_CLAMP_EXT 0x8E1B
	void glPolygonOffsetClampEXT (GLfloat factor, GLfloat units, GLfloat clamp)