Adds the Deque interface, and allows LinkedList to implement that interface.

This also changes ConcurrentLinkedQueue to implement the Queue interface, and just throw exceptions for operations which are not currently implemented.
Interfaces and the foundation for a ReentrantLock implementation
Add parkBlocker variable to Thread.java
Fix for travis build failure for needing to initialize the new field in Thread.
Merge pull request #189 from jentfoo/interface_improvements

interface improvements and LockSupport implementation