Add role-based permission to Tidy filter module

whitespace problem - looks like a tab in hook_perm

Add doxygen comments indicating which hooks are being implemented.

improve form_id check

The code looks good, but the comments aren't exactly the right format. They should look something like this:

/**
 * Implementation of hook_perm().
 */

Of course the asterisks should align vertically. Otherwise I tested the code and it works fine. Attached is a patch that corrects the comment format.

patch looks fine visually

Committed.