advance (Imlib2::Font)

    /*
     * Get the horizontal and vertical advance of the given string using
     * this font.
     *
     * Example:
     *   font = Imlib2::Font.new 'verdana/36'
     *   advances = font.advance "what's my advance?"
     *   ['horizontal', 'vertical'].each_index { |i, v|
     *     puts 'text ' << v << ' advance = ' << advances[i]
     *   }
     *
     */
    static VALUE font_text_advance(VALUE self, VALUE text) {