save (Imlib2::Image)

    /*
     * Save an Imlib2::Image to a file (throws an exception on error).
     *
     * Examples:
     *   image.save 'output_file.png'
     *
     *   filename = 'output_file.jpg'
     *   begin
     *     image.save filename
     *   rescue Imlib2::FileError
     *     $stderr.puts "Couldn't save file \"#{filename}\": " + $!
     *   end
     *
     */
    static VALUE image_save(VALUE self, VALUE val) {