RFR(s): JDK-8203184 List.copyOf() fails to copy sublists

[Stuart Marks]

Hi all,

Please review this small changeset that restores copy semantics to List.copyOf() 
when applied to a sublist of an unmodifiable list.

Webrev:

    http://cr.openjdk.java.net/~smarks/reviews/8203184/webrev.0/

Bug:

    https://bugs.openjdk.java.net/browse/JDK-8203184

Thanks,

s'marks