Begin cleaning up the RADIUS constant documentation as part of the 1.3.0 update.

I'm only about half done, but my motivation is dipping a little, so I'm going
to document the other 1.3.0 features and come back to this tomorrow.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@330789 c90b9560-bf6c-de11-be94-00142212c4b1