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/plugins.class.php

@@ -69,7 +69,7 @@ class plugins
   /**
    * Initialize $fs_plugins and $db_plugins_by_id
    */
-  function plugins()
+  function __construct()
   {
     $this->get_fs_plugins();
 
@@ -716,4 +716,4 @@ DELETE FROM '. PLUGINS_TABLE .'
     $this->fs_plugins = $active_plugins + $inactive_plugins + $not_installed;
   }
 }
-?>
+?>