#54 import latest CHMv8 code from Concurrency JSR-166 Interest Site (http://gee.cs.oswego.edu/dl/concurrency-interest/index.html)

Original CVS versions:
ConcurrentHashMap.java    : 1.257
CountedCompleter.java     : 1.47
ForkJoinPool.java         : 1.225
ForkJoinTask.java         : 1.89
ForkJoinWorkerThread.java : 1.65
ThreadLocalRandom.java    : 1.29
 #54 port CHMv8 code + add our tests