GL_SGIS_sharpen_texture
http://oss.sgi.com/projects/ogl-sample/registry/SGIS/sharpen_texture.txt
	void glGetSharpenTexFuncSGIS (GLenum target, GLfloat* points)
	void glSharpenTexFuncSGIS (GLenum target, GLsizei n, const GLfloat* points)