Cleanup warnings in the j.u.c. package.
This is a sync up with the warning fixes in Doug's CVS. There are also a few style cleanups, import fixes, trivial local variable renaming, typos, etc. But nothing too surprising!
http://cr.openjdk.java.net/~chegar/7118066/webrev.00/webrev/ -Chris.P.S. I have already reviewed this, and the contribution is of course from Doug.
