Function gl::CopyTextureSubImage2D

pub unsafe fn CopyTextureSubImage2D(texture: GLuint,
                                    level: GLint,
                                    xoffset: GLint,
                                    yoffset: GLint,
                                    x: GLint,
                                    y: GLint,
                                    width: GLsizei,
                                    height: GLsizei)