Request for review (M) - 6984287

[Jon Masamitsu]

Fixed 6984287: Clean up how GC parallel workers are specified.

The significant changes are to move toward making the number of
GC workers part of the workgang and not part of the task.  Also
made some changes to balancing queues for parallel Reference
processing.  Many, many of the other changes are a name change
or a call to a function instead of the direct use of a command line
flag.

http://cr.openjdk.java.net/~jmasa/6984287/webrev.00/