Eliminate dependency from PolicyFile to com.sun.security.auth.PrincipalComparator

The support for the com.sun.security.auth.PrincipalComparator class in the sun.security.provider.PolicyFile implementation was only for compatibility with principal subclasses that were originally implemented for legacy JAAS policy files.

It would be nice to eliminate this dependency:
  sun.security.provider.PolicyFile -> com.sun.security.auth.PrincipalComparator

so that the com.sun.security.auth package can be moved entirely to the jaas module which is not really needed in the base module.