It looks like the "Getting Started" documentation page is out of date.
Code:
	{
		using namespace clan;
		DisplayWindow window("Hello World", 640, 480);
		Canvas canvas(window);
		InputDevice keyboard = window.get_ic().get_keyboard();
		clan::Font font(canvas, "Tahoma", 30); // The clan prefix is required on linux due to a namespace conflict

		while (!keyboard.get_keycode(keycode_escape)) {
			canvas.clear(Colorf::cadetblue);
			canvas.draw_line(0, 110, 640, 110, Colorf::yellow);
			font.draw_text(canvas, 100, 100, "Hello World!", Colorf::lightseagreen);
			canvas.flush();
			window.flip();
			KeepAlive::process();
		}
	}
Changes were: "Canvas canvas(window);"
and "canvas.draw_line(0, 110, 640, 110, Colorf::yellow);"