Fixed a very obscure bug that would cause certain versions of PHP crash on Windows systems when one of the menu items had an absolute file name set as a slug and open_basedir is enabled. See code for a more detailed explanation.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@967394 b8457f37-d9ea-0310-8a92-e5e31aec5664