The memfree item with threshold

[yy963]

The swapfree and memfree codes is diffrent，but their the logic of the judgement is the same，and the result should be same
I modify follows：

if ($plugin->opts->item eq 'memfree') {

# -- add 100 - make the free become avaliable
$data_val = 100 - getPercentage('memtotal',$data_val);

}

if($plugin->opts->item eq 'memfree') {
$plugin->set_thresholds(warning => (100 - $plugin->opts->warning), critical => (100 - $plugin->opts->critical));

   # -- add 2 lines make the display value and actual match  
    $output_val = 100-$data_val;
    $output_text = $plugin->opts->item . " = " . $output_val;

} else {
$plugin->set_thresholds(warning => $plugin->opts->warning, critical => $plugin->opts->critical);
}