Fix a bug where a hidden submenu page with an URL like "options-general.php?page=something" would still be accessible via "admin.php?page=something". 
 
 WordPress has some special-case code that lets people access hook-based admin pages either via their canonical parent page (options-general.php, plugins.php, index.php, etc) or the special admin.php file. Previously, AME would only recognize the canonical version. This change adds an extra check for alternative paths.
  
  Note that we still only check current[alt] vs item[path] but not current[path] vs item[alt]. Generating an alt path for every single menu item could be complicated/slow.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@873317 b8457f37-d9ea-0310-8a92-e5e31aec5664