RFR 8005311: Add Scalable Updatable Variables, DoubleAccumulator, DoubleAdder, LongAccumulator, LongAdder

[Chris Hegarty]

Updated webrev and javadoc:
   http://cr.openjdk.java.net/~chegar/8005311/ver.01/

I plan to finalize the API based on this updated version.

Note: the links in the javadoc do not work. It is simply the way that I 
copied the html files. I verified that they all link correctly in a full 
docs build.

-Chris.