Locking: Add contin tracing to detect deadlocks

We added the code to trace all the contins linked to a particular
Lockvoker, into SerializedAsyncContinuation. This basically
ensures that we'll almost never deal with a deadlock. So cool.

include/asynchronousContinuation.h

@@ -38,7 +38,6 @@ public:
 		std::shared_ptr<AsynchronousContinuation<OriginalCbFnT>>
 			lifetimePreservingConveyance);
 
-
 	/**	EXPLANATION:
 	 * When an exception is thrown in a an async callee, which pertains to an
 	 * error in the data given by the caller, we ought not to throw the
@@ -67,6 +66,11 @@ public:
 			{ std::rethrow_exception(exception); }
 	}
 
+	// Implement the virtual method from AsynchronousContinuationChainLink
+	virtual std::shared_ptr<AsynchronousContinuationChainLink>
+	getCallersContinuation() override
+		{ return originalCallback.callerContinuation; }
+
 public:
 	Callback<OriginalCbFnT> originalCallback;
 	std::exception_ptr exception;