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
fix Class.getDeclaredMethods

getDeclaredMethods was returning methods which were inherited from
interfaces but not (re)declared in the class itself, due to the VM's
internal use of VMClass.methodTable differing from its role in
reflection.  For reflection, we must only include the declared
methods, not the inherited but un-redeclared ones.

Previously, we saved the original method table in
ClassAddendum.methodTable before creating a new one which contains
both declared and inherited methods.  That wasted space, so this patch
replaces ClassAddendum.methodTable with
ClassAddendum.declaredMethodCount, which specifies how many of the
methods in VMClass.methodTable were declared in that class.

Alternatively, we could ensure that undeclared methods always have
their VMMethod.class_ field set to the declaring class instead of the
inheriting class.  I tried this, but it led to subtle crashes in
interface method lookup.  The rest of the VM relies not only on
VMClass.methodTable containing all inherited interface methods but
also that those methods point to the inheriting class, not the
declaring class.  Changing those assumptions would be a much bigger
(and more dangerous in terms of regression potential) effort than I
care to take on right now.  The solution I chose is a bit ugly, but
it's safe.