RFR 8005704: Update ConcurrentHashMap to v8

[Chris Hegarty]

Since my previous failed attempt to update the j.u.c. world, this review 
is for the update to j.u.c.ConcurrentHashMap v8 from Doug's CVS.

http://cr.openjdk.java.net/~chegar/8005704/ver.00/specdiff/java/util/concurrent/package-summary.html
http://cr.openjdk.java.net/~chegar/8005704/ver.00/webrev/

A few initial comments:

1) CHM no longer extends AbstractMap. I guess this should not be a
    problem in the real world, and I guess users would not be too
    surprised by instanceof checks. Just worth highlighting the change
    for compatibility.

2) KeySetView.spliterator()

    I guess the API should also report CONCURRENT, NONNULL & SUBSIZED?
    And the implementation should return SIZED too?

3) Value/EntrySpliterator.spliterator() should return SIZED?

4) Does is make sense for KeySetView to be Serializable? It looks a
    little odd with value as its only field.

-Chris.