bug #385 compatibility with PHP7

* replace old-style constructor with PHP5-style constructor (__construct)
* do not call set_magic_quotes_runtime() any longer
* avoid automatic conversion from array to string

admin/include/themes.class.php

@@ -60,7 +60,7 @@ class themes
   /**
    * Initialize $fs_themes and $db_themes_by_id
   */
-  function themes()
+  function __construct()
   {
     $this->get_fs_themes();
 
@@ -736,4 +736,4 @@ SELECT
   }
 
 }
-?>
+?>