RFR 8005819: Support cross-realm MSSFU

[Martin Balao]

Hi,

I'd like to propose Webrev.00 for JDK-8005819 [1]:

 * http://cr.openjdk.java.net/~mbalao/webrevs/8005819/8005819.webrev.00/

Implementation is based in the MS-SFU document [2].

Testing

 * ReferralsTest extended to support S4U2Self and S4U2Proxy referrals

 * No regressions found in jdk/sun/security/krb5 category

 * Tested against a real Active Directory 2016 setup, with 2 referral hops
  * Note: I can provide a PCAP capture and my internal test code if
there is interest

Thanks,
Martin.-

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[1] - https://bugs.openjdk.java.net/browse/JDK-8005819
[2] -
https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-sfu/3bff5864-8135-400e-bdd9-33b552051d94