interface improvements and LockSupport implementation

I have started implementing a ReentrantLock and a ReentrantReadWriteLock.  Those are not ready to merge yet, but these are some auxiliary things that I had to do first in order to implement those (which I think _are_ ready to merge).

Changes are as follows:
* Added Deque interface to classpath
* LinkedList now implements the Deque (previously it was not even implementing Queue)
* ConcurrentLinkedQueue now implements the Queue interface (but just throws UnsupportedOperationExceptions for things not implemented yet)
* Added interfaces in java.util.concurrent.locks
* Added a fully implemented LockSupport (though not used or tested yet).

I plan to have LockSupport unit tested and used once we add ReentrantLock and ReentrantReadWriteLock.  But let me know if you guys feel like we need unit testing directly on LockSupport (it mostly is just deferring to Unsafe).

If desired we can wait to merge this till we have the ReentrantLock and ReentrantReadWriteLock ready.  I am just worried I may not have time to finish them soon, and this work seems like it is ready and useful.  Let me know your thoughts.