Async: add sh_ptr<ContinuationChainLink> to Callback<>

This change enables us to finally implement the tracing of
continuations backward from the point of acquisition for deadlock
debugging.

include/serializedAsynchronousContinuation.h

@@ -11,6 +11,7 @@
 #include <lockSet.h>
 #include <asynchronousContinuation.h>
 #include <lockerAndInvokerBase.h>
+#include <callback.h>
 
 namespace smo {
 
@@ -21,7 +22,7 @@ class SerializedAsynchronousContinuation
 public:
 	SerializedAsynchronousContinuation(
 		const std::shared_ptr<ComponentThread> &caller,
-		OriginalCbFnT originalCbFn,
+		Callback<OriginalCbFnT> originalCbFn,
 		std::vector<std::reference_wrapper<SpinLock>> requiredLocks = {})
 	:	PostedAsynchronousContinuation<OriginalCbFnT>(caller, originalCbFn),
 		requiredLocks(*this, std::move(requiredLocks))