[8] Code Review Request for 7019834: Eliminate dependency from PolicyFile to com.sun.security.auth.PrincipalComparator

[Sean Mullan]

As part of the effort to prepare the platform for modules (see 
http://openjdk.java.net/jeps/162) we need to remove or deprecate 
undesirable dependencies. One of these is the dependency:

  sun.security.provider.PolicyFile -> 
com.sun.security.auth.PrincipalComparator

which is problematic since the com.sun.security.auth package is not 
intended to be part of the base module.

The solution is to add an implies method to the java.security.Principal 
interface. Existing PrincipalComparator implementations must also 
implement Principal if they are to be used by the default "JavaPolicy" 
Policy implementation. This change will allow us to remove the 
dependency on the PrincipalComparator class and preserve compatibility.

Since java.security.Principal is an interface, this change requires the 
new default method feature of lambda.

webrev: http://cr.openjdk.java.net/~mullan/webrevs/7019834/webrev.00/

Thanks,
Sean