RFR [9] - 8060052: FutureTask; fix underflow when timeout = Long.MIN_VALUE

[Chris Hegarty]

This is a formal review request for pulling the latest FutureTask from 
the 166 CVS.

Webrev:
    http://cr.openjdk.java.net/~chegar/8060052/webrev.00/webrev/

The most significant issue being addresses is that 
task.get(Long.MIN_VALUE, NANOSECONDS) does not timeout for a really 
really long time, when it should throw TimeoutException almost 
immediately. There is some other refactoring around consistent usage of 
Unsafe.

I took the liberty of adding a trivial test to give addition coverage in 
OpenJDK, but there is a TCK test in the 166 CVS that exercises this, and 
in fact the sync'ing of that test into the JCK 9 ea is what promoted 
this RFR.

-Chris.