RFR 7118066: Warnings in java.util.concurrent package

[Chris Hegarty]

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.