Add basic structure for fuzzing targets

General changes:

* Add -D/--deterministic command line option as
  convenience/alternative to -G/--load-seeds (i.e. no file needed, it just
  uses zero-initialized random seeds).  It also changes Broker data
  stores over to using deterministic timing rather than real time.

* Add option to make Reporter abort on runtime scripting errors

src/Sessions.h

@@ -72,6 +72,9 @@ public:
 	// that are still active.
 	void Drain();
 
+	// Clears the session maps.
+	void Clear();
+
 	void GetStats(SessionStats& s) const;
 
 	void Weird(const char* name, const Packet* pkt,