I've just commited new version of langdoc.php into both HEAD and MOODLE_15_STABLE branches. It includes fix by Jaime Villate - Sunday, 8 May 2005, 10:45 PM and works for me with all these problematic strings:
<>
< >
c:\apache
<? phpinfo(); ?>
Languages
landoc.php seem to be deleting backslash
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