Reimplementation of strcasecmp()

Reimplementation of strcasecmp() using collator.
It uses the same implementation already made for strcmp().
Fix of menuSort() function in "Ui/Admin.php".

Screens fixed:
- Administration

inc/Ui/Admin.php

@@ -159,7 +159,7 @@ protected function getPluginList() {
      * @return int
      */
     protected function menuSort($a, $b) {
-        $strcmp = strcasecmp($a['prompt'], $b['prompt']);
+        $strcmp = strcompare($a['prompt'], $b['prompt']);
         if($strcmp != 0) return $strcmp;
         if($a['sort'] === $b['sort']) return 0;
         return ($a['sort'] < $b['sort']) ? -1 : 1;

inc/sort.php

@@ -70,14 +70,15 @@ function natural_sort(&$files_or_dirs){
 }
 
 /**
- * Replacement for strcmp() in fulltext.php, line 373.
+ * Replacement for strcmp() in fulltext.php, line 373, where all strings are lowercase.
+ * Replacement for strcasecmp() in Ui/Admin.php, line 162.
  */
 function strcompare($first, $second){
     global $collator;
     _init_collator();
 
     if(!isset($collator))
-        return strcmp($first, $second);
+        return strcasecmp($first, $second);
     else
         return $collator->compare($first, $second);
 }