Add baggage swap operation

include/baggage.h

@@ -67,6 +67,7 @@ namespace ThreadLocalBaggage {
 	void Delete();                       // Delete the current thread's baggage
 	void Set(Baggage new_baggage);       // Set the current thread's baggage to the provided baggage, destroying the previous baggage
 	void Join(Baggage &otherBaggage);    // Merge the current thread's baggage with the provided baggage
+	Baggage Swap (Baggage otherBaggage); // Set the current thread's baggage to the provided baggage, and return the previous baggage
 
 }
 

src/thread_local_baggage.cpp

@@ -25,6 +25,12 @@ void ThreadLocalBaggage::Set(Baggage new_baggage) {
 	current_threads_baggage = new_baggage; 
 }
 
+Baggage ThreadLocalBaggage::Swap(Baggage other_baggage) {
+	Baggage prev = current_threads_baggage;
+	current_threads_baggage = other_baggage;
+	return prev;
+}
+
 void ThreadLocalBaggage::Delete() {
 	current_threads_baggage = Baggage();	
 }