bug 3201: accept - in plugin directory name (identifier)

git-svn-id: http://piwigo.org/svn/trunk@30979 68402e56-0260-453c-a942-63ccdbb3a9ee

admin/plugin.php

@@ -46,7 +46,7 @@ if (count($sections)<2)
 
 $plugin_id = $sections[0];
 
-if (!preg_match('/^\w+$/', $plugin_id))
+if (!preg_match('/^[\w-]+$/', $plugin_id))
 {
   die('Invalid plugin identifier');
 }