Review Request for 7026255 : Methods of Subject that throw SecurityException do not specify what permissions are required

[Sean Mullan]

This is a clarification in the javax.security.auth.Subject javadocs to 
indicate what permissions are required for methods that throw 
SecurityException:

http://cr.openjdk.java.net/~mullan/webrevs/7026255/webrev.00/

I also took the opportunity to fix a couple of other minor issues: added 
@Override annotations, removed spurious <p> tags, and changed @exception 
to @throws.

Thanks,
Sean