RFR: 8015081

[Jamil Nimeh]

Hello all,

This revision for the fix for 8015081 has the following test changes:

Removal of the static byte buffers for serialized data in lieu of a more 
dynamic approach.  A stripped down version of Subject in its own package 
is now being compiled alongside SubjectNullTests.java. This version of 
Subject allows the creation and serialization of Subjects with null 
elements in the principals SecureSet. Immediately following 
serialization, this special Subject's class designation is overwritten 
to be javax.security.auth.Subject.  When deserialization occurs, the 
correct (JDK 9) version of Subject will be used and null element checks 
will take place.

Thanks go to Weijun Wang for this testing approach.

http://cr.openjdk.java.net/~weijun/8015081/webrev.07

--Jamil