review request (S) - 6821693: TaskQueue capacity

[John Coomes]

I'd appreciate some reviews of 

http://cr.openjdk.java.net/~jcoomes/6821693-taskqueue64/

	6821693 64-bit TaskQueue capacity still too small
	6821507 Alignment problem in GC taskqueue

Those w/good memories may recall an earlier review request, but enough
code has changed and time has passed to require new reviews.

A micro-test that pushes/pops items on/off the queue is ~10% faster
w/the new code on intel, but there's no noticeable effect on
real-world apps.

-John